The Xbox is a home video game console manufactured by Microsoft that is the first installment in the Xbox series of video game consoles. It was released as Microsoft's first foray into the gaming console market on November 15, 2001, in North America, followed by Australia, Europe and Japan in 2002. It is classified as a sixth-generation console, competing with Sony's PlayStation 2, Sega's Dreamcast and Nintendo's GameCube. It was also the first major console produced by an American company since the release of the Atari Jaguar in 1993.

The console was announced in March 2000. With the release of the PlayStation 2, which featured the ability to playback CD-ROMs and DVDs in addition to playing games, Microsoft became concerned that game consoles would threaten the personal computer as an entertainment device for living rooms. Whereas most games consoles to that point were built from custom hardware components, the Xbox was built around standard personal computer components, using variations of Microsoft Windows and DirectX as its operating system to support games and media playback, and featuring a 733 MHz Intel Pentium III CPU and a 233 MHz Nvidia GeForce 3-based NV2A GPU, the latter two making the Xbox technically more powerful compared to its rivals. The Xbox was the first console to feature a built-in hard disk. The console also was built with direct support for broadband connectivity to the Internet via an integrated Ethernet port, and with the release of Xbox Live, a fee-based online gaming service, a year after the console's launch, Microsoft gained an early foothold in online gaming and made the Xbox a strong competitor in the sixth generation of consoles. The popularity of killer app blockbuster titles such as Bungie's Halo 2 contributed to the popularity of online console gaming, and in particular first-person shooters.

The Xbox had a record-breaking launch in North America, selling 1.5 million units before the end of 2001, aided by the popularity of one of the system's launch titles, Halo: Combat Evolved, which sold a million units by April 2002. The system went on to sell a worldwide total of 24 million units, including 16 million in North America; however, Microsoft was unable to make a steady profit off the console, which had a manufacturing price far more expensive than its retail price, despite its popularity, losing over $4 billion during its market life. The system outsold the GameCube and the Sega Dreamcast, but was vastly outsold by the PlayStation 2, which had sold over 155 million units by the system's end of production. It also underperformed outside of the Western market; particularly, it sold poorly in Japan due to its large console size and an overabundance of games marketed towards American audiences instead of Japanese-developed titles. Production of the system was discontinued starting in 2005. The Xbox was the first in an ongoing brand of video game consoles developed by Microsoft, with a successor, the Xbox 360, launching in November 2005, followed by the Xbox One in 2013 and the Xbox Series X and Series S consoles in 2020.

Before the Xbox, Microsoft had found success publishing video games for its Windows PCs, releasing popular titles such as Microsoft Flight Simulator and the massively successful Age of Empires after the creation of DirectX, the application programming interface (API) that allowed for direct access of the computer hardware and bypassing Windows. However, the company had not entered the home console market of video games, which was dominated at the time by Sony's PlayStation. Sony was working on its next video game console, the PlayStation 2 (PS2), announced officially to the public on March 2, 1999, and intended for the system to act as a gateway for all types of home entertainment. Sony presented a vision where the console would ultimately replace the desktop computer in the home. Microsoft CEO Bill Gates saw the upcoming PS2 as a threat to Microsoft's line of Windows PCs, worrying that the all-encompassing system could eliminate consumer interests in PCs and drive them out of the market. With video games rapidly growing into a massive industry, Gates decided that Microsoft needed to venture into the console gaming market to compete with Sony. Previously, Sega had developed a version of Windows CE for its Dreamcast console to be used by game developers. Additionally, Gates had directly approached Sony CEO Nobuyuki Idei before the public announcement of the PS2 regarding letting Microsoft develop programming software for the console. However, the offer was declined by Idei in favor of having Sony create proprietary software. Microsoft had also attempted to meet with Hiroshi Yamauchi and Genyo Takeda of Nintendo to potentially acquire the company, but Nintendo declined to go further.

In 1998, four engineers from Microsoft's DirectX team—Kevin Bachus, Seamus Blackley, Ted Hase and DirectX team leader Otto Berkes—began discussing ideas for a new console which would run off Microsoft's DirectX technology. Nat Brown, the Windows Software Architect at Microsoft, would also become a regular contributor to the project after meeting Hase in November 1998. The project was codenamed "Midway," in reference to the Battle of Midway during World War II in which Japan was decisively defeated by American forces, as a representation of Microsoft's desire to surpass Sony in the console market. The DirectX team held their first development meeting on March 30, 1999, in which they discussed issues such as getting a PC to boot at a quicker pace than usual. The console would run off Windows 2000 using DirectX 8.1, which would allow PC developers to easily transition into making games for the console while also granting it a larger processing power than that of most other home consoles. According to Blackley, using PC technology as the foundation for a video game console would eliminate the technological barriers of most home consoles, allowing game creators to expand further on their own creativity without having to worry about hardware limitations.

The 4 DirectX team members encountered disagreements with the Silicon Valley engineering team behind WebTV, which joined Microsoft after they purchased the rights to the device. Microsoft executive Craig Mundie wanted the project to be led by the WebTV team, who believed the console should be built from the ground-up as an appliance running off Windows CE; however, the DirectX team were adamant about the idea of repurposing PC hardware components, such as a hard disk drive, arguing that they were cheaply manufactured and could easily be updated every year. The 4 developers gained the support of Ed Fries, the head of Microsoft's gaming division, who believed the use of a hard drive, in particular, would give the console a technical edge among competitors despite its high manufacturing cost. The two opposing teams pitched their arguments to Gates on May 5, 1999, at a meeting attended by over twenty different people. WebTV's team, among whom were Nick Baker, Dave Riola, Steve Perlman, and Tim Bucher, and their sponsor, Craig Mundie, made the case that creating an appliance would be far cheaper, highlighting that most consoles were generally sold at around $300. They also wanted to use a custom-made graphics chip, which could be shared across several different home devices. Conversely, Fries, vouching for the DirectX team, argued that using a PC hard drive would set Microsoft's console apart from competitors by allowing for the direct implementation of online access, an argument which Gates sided with. When Gates questioned if PC games could be effectively ported to the new console, Blackley explained that the machine would utilize DirectX hardware, meaning that they could be converted easily. Gates heavily favored this proposition over WebTV's, whose concept relied on Windows CE, a heavily stripped-down Windows variant that was not compatible with DirectX. As such, Gates sided with the DirectX concept and gave Berkes' team permission to create a new video game console. Despite this, WebTV would still play a part in the Xbox's initial launch.

Rick Thompson and Robert J. Bach were responsible for overseeing the Xbox's design. The DirectX team began constructing prototype consoles, purchasing several Dell computers and using their internal parts. Initially, it envisioned that after designing the console, Microsoft would have worked with a third-party computer manufacturer to mass-produce the units. However, the early work showed that this would need to be something that Microsoft would have to produce themselves, making the prospect a far more costly operation; the name "Coffin Box" became associated with the project as there were fears the project would end careers at Microsoft. Further, as a gaming console, they could not provide the direct Windows interface to users. While Thompson and Bach had warned Gates and Steve Ballmer about these large-scale changes from the initial proposal in late 1999, the matter came to a head at a February 14, 2000, meeting, informally referred to as the Valentine's Day Massacre, in which Gates furiously vented about the new cost proposal and massive changes in this console from what had been previously presented, since the Xbox appeared to marginalize Windows. However, after being reminded that this was a product to compete against Sony, Gates and Ballmer gave the project the go-ahead along with the necessary marketing budget. Another contentious point of design was the addition of Ethernet connectivity rather than simple support for dial-up networking. At this point, most consumer homes had access to Internet connectivity, but social networks had yet to be established which would later demonstrate the viability of this decision. The Xbox leads argued that with the planned Xbox Live functionality, the Ethernet port would help friends be able to play after they have graduated from schools and colleges and moved across the country.

Throughout the console's prototyping, Microsoft was working with AMD for the CPU on the system. According to Blackley, just prior to the system's reveal in January 2001, the Microsoft engineers opted to switch to an Intel CPU, a fact that had not yet been communicated to AMD prior to the reveal.

Among the names considered for the new console were a number of acronyms, including "Windows Entertainment Project" (WEP), "Microsoft Total Gaming" (MTG), "Microsoft Interactive Network Device" (MIND), and "Microsoft Interactive Center" (MIC). Also among the names considered was "DirectX Box", referring to the system's reliance on Direct X. At one point, Hase jokingly came up with the names "XXX-Box" and "DirectXXX-Box" as a nod to the system's higher volume of adult content compared to Sony or Nintendo's consoles. "DirectX Box" was quickly shortened to "Xbox" through an e-mail conversation, and was ultimately favored by the development team, though a number of spelling variants were tossed around, such as xBox, XboX, and X-box. Microsoft's marketing department did not like this name, suggesting "11-X" or "Eleven-X" as alternatives. During focus testing, the company put the name "Xbox" on the list of possible names simply to prove how unpopular the Xbox name would be with consumers. However, "Xbox" proved to be the more popular name on the list and was thus selected as the official name of the product.

When the physical design of the controller began, circuit boards for the controller had already been manufactured. Microsoft had asked Sony's supplier, Mitsumi Electric, for a similar folded and stacked circuit board design used in Sony's DualShock 2 controller, but the company refused to manufacture such a design for Microsoft. This led to the controller being bulky and nearly three times the size of Sony's controller. This initial controller design was never launched in Japan. The console instead launched with a smaller, redesigned version named "Controller S" that did use the more compact circuit board design.

As the development team began to tighten down the design of the Xbox, they got help from Flextronics not only in revising the design but in mass production, creating a factory in Guadalajara, Mexico, for this purpose. Early production units had a high failure rate of around 25%, which Flextronics repaired. Later iterations of the hardware design worked to eliminate these failures.

Gates first publicly mentioned the Xbox in an interview in late 1999, stating that he wanted the system "to be the platform of choice for the best and most creative game developers in the world". It was later announced officially by Gates in a keynote presentation at the Game Developers Conference in San Jose on March 10, 2000, showing off an early prototype build of the system and a series of demos showcasing its hardware. The presentation and the new system were well-received, impressing developers with both the hard drive and the Ethernet port and appealing to them with the notion of easy-to-use development tools.

Microsoft began looking at a series of acquisitions and partnerships to secure content for the console at this time. In early 2000, Sega's Dreamcast sales were diminishing, in part due to Electronic Arts' decision to bypass the console, and Sony's PlayStation 2 was just going on sale in Japan. Gates was in talks with Sega's late chairman Isao Okawa about the possibility of Xbox compatibility with Dreamcast games, but negotiations fell apart over whether the Dreamcast's SegaNet online service should be implemented. Microsoft also looked to acquire Electronic Arts, Nintendo, Square Enix, and Midway without success. The company did achieve success in convincing developers at Bethesda Game Studios and Tecmo about the power of the Xbox over the PS2, lining up The Elder Scrolls III: Morrowind and Dead or Alive 3 as Xbox console-exclusives.

Around this same time, Microsoft announced it was rebranding its Games Group, which had been focused on developing games for Windows, to the Microsoft Games division to make titles for both Windows and the Xbox. Microsoft began acquiring a number of studios to add to the division, notably Bungie in June 2000, shortly after their announcement of Halo: Combat Evolved. With Microsoft's acquisition, Halo switched from being a release for personal computers to being an Xbox exclusive release and as a launch time to help drive sales of the console.

The Xbox was officially unveiled to the public by Gates and guest professional wrestler Dwayne "The Rock" Johnson at CES 2001 in Las Vegas on January 3, 2001. Microsoft announced Xbox's release dates and prices at E3 2001 in May. Most Xbox launch titles were unveiled at E3, most notably Halo and Dead or Alive 3.

The unit's release in November 2001 was partially hampered by the impact of the September 11 attacks on travel, as Microsoft could not travel to the Guadalajara facility to help test units. They were able to arrange to ship the units locally instead of testing at Microsoft facilities to have them ready for launch.

The system was officially launched at midnight on November 15, 2001, three days before the subsequent launch of the Nintendo GameCube. A special event was held on the prior night as part of the grand opening of the flagship store of Toys 'R' Us at Times Square in New York City, in which 1,000 systems were shipped to the store to kick off sales. Bill Gates was present at the event, personally selling the first Xbox console and greeting people in line and playing games with them at the numerous display units present.

In 2002, the Independent Television Commission (ITC) banned a television advertisement for the Xbox in the United Kingdom after complaints that it was "offensive, shocking and in bad taste." It depicted a mother giving birth to a baby boy, fired like a projectile through a window, aging rapidly as he flies through the air. The advertisement ends with an old man crash-landing into his own grave and the slogan, "Life is short. Play more."

The Xbox's successor, the Xbox 360, was officially announced on May 12, 2005 on MTV. It was the first next generation system to be announced. It was released in North America on November 22, 2005. Nvidia ceased production of the Xbox's GPU in August 2005, which marked the end of brand-new Xbox production. The last game for the Xbox in Japan was The King of Fighters Neowave released in March 2006, the last Xbox game in Europe was Xiaolin Showdown released in June 2007, and the last game in North America was Madden NFL 09 released in August 2008. Support for out-of-warranty Xbox consoles was discontinued on March 2, 2009. Support for Xbox Live on the console ended on April 15, 2010.

The Xbox 360 supports a limited number of the Xbox's game library if the player has an official Xbox 360 Hard Drive. Xbox games were added up until November 2007. Xbox game saves cannot be transferred to Xbox 360, and the ability to play Xbox games through Xbox LIVE has been discontinued since April 15, 2010. It is still possible to play Xbox games with System Link functionality online via both the original console and the Xbox 360 with tunneling software such as XLink Kai. It was announced at E3 2017 that the Xbox One would be gaining support for a limited number of the Xbox's game library.

The Xbox was the first video game console to feature a built-in hard disk drive, used primarily for storing game saves and content downloaded from Xbox Live. This eliminated the need for separate memory cards (although some older consoles, such as the Amiga CD32, used internal flash memory, and others, such as the TurboGrafx-CD, Sega CD, and Sega Saturn, had featured built-in battery backup memory prior to 2001). An Xbox user could rip music from standard audio CDs to the hard drive, and these songs were used for the custom soundtracks in some games.

Unlike the PlayStation 2, which could play movie DVDs without the need for a remote control (although an optional remote was available), the Xbox required an external IR adapter to be plugged into a controller port in order to play movie DVDs. If DVD playback is attempted without the IR sensor plugged in, an error screen will pop up informing the user of the need for the Xbox DVD Playback Kit. The said kit included the IR sensor and a remote control (unlike the PS2, the Xbox controller could not control DVD playback). Said remote was manufactured by Thomson (which also manufactured optical drives for the console) and went on sale in late 2002, which meant a modified version of the remote design used by the RCA, GE and ProScan consumer electronics of the era was used for the Xbox remote, and therefore users wishing to use a universal remote were instructed to utilize RCA DVD remote codes.

The Xbox was the first console to feature Dolby Interactive Content-Encoding Technology, which enables real-time Dolby Digital encoding. Previous game consoles could only use Dolby Digital 5.1 during non-interactive "cut scene" playback.

The Xbox is based on commodity PC hardware and is much larger and heavier than its contemporaries. This is largely due to a bulky tray-loading DVD-ROM drive and the standard-size 3.5-inch hard drive. The Xbox has also pioneered safety features, such as breakaway cables for the controllers to prevent the console from being pulled from the surface upon which it rests.

Several internal hardware revisions have been made in an ongoing battle to discourage modding (hackers continually updated modchip designs in an attempt to defeat them), to cut manufacturing costs, and to make the DVD-ROM drive more reliable (some of the early units' drives gave disc-reading errors due to the unreliable Thomson DVD-ROM drives used). Later-generation units that used the Thomson TGM-600 DVD-ROM drives and the Philips VAD6011 DVD-ROM drives were still vulnerable to failure that, respectively, either rendered the consoles unable to read newer discs or caused them to halt the console with an error code usually indicating a PIO/DMA identification failure. These units were not covered under the extended warranty.

In 2002, Microsoft and Nvidia entered arbitration over a dispute on the pricing of Nvidia's chips for the Xbox. Nvidia's filing with the SEC indicated that Microsoft was seeking a $13 million discount on shipments for NVIDIA's fiscal year 2002. Microsoft alleged violations of the agreement the two companies entered, sought reduced chipset pricing, and sought to ensure that Nvidia fulfill Microsoft's chipset orders without limits on quantity. The matter was privately settled on February 6, 2003.

The Xbox includes a standard AV cable which provides composite video and monaural or stereo audio to TVs equipped with RCA inputs. European Xboxes also included an RCA jack to SCART converter block and the standard AV cable.

An 8 MB removable solid-state memory card can be plugged into the controllers, onto which game saves can either be copied from the hard drive when in the Xbox dashboard's memory manager or saved during a game. Most Xbox game saves can be copied to the memory unit and moved to another console, but some Xbox saves are digitally signed. It is also possible to save an Xbox Live account on a memory unit, to simplify its use on more than one Xbox. The ports at the top of the controllers could also be used for other accessories, primarily headsets for voice chat via Xbox Live.

The Xbox CPU is a 32-bit 733 MHz, custom Intel Pentium III Coppermine-based processor. It has a 133 MHz 64-bit GTL+ front-side bus (FSB) with a 1.06 GB/s bandwidth. The system has 64 MB unified DDR SDRAM, with a 6.4 GB/s bandwidth, of which 1.06 GB/s is used by the CPU and 5.34 GB/s is shared by the rest of the system.

Its GPU is Nvidia's 233 MHz NV2A. It is capable of geometry calculations for up to a theoretical 115 million vertices/second. It has a peak fillrate of 932 megapixels/second, capable of rendering a theoretical 29 million 32-pixel triangles/second. With bandwidth limitations, it has a realistic fillrate of 250–700 megapixels/second, with Z-buffering, fogging, alpha blending, and texture mapping, giving it a real-world performance of 7.8–21 million 32-pixel triangles/second.