"Where No One Has Gone Before" is the sixth episode of the American science-fiction television series Star Trek: The Next Generation, which originally aired October 26, 1987, in broadcast syndication in the United States. A high-definition, remastered version of the episode received a limited theatrical release for one day (along with the episode "Datalore") to celebrate the 25th anniversary of the series on July 23, 2012. The story was originally developed with the title "Where None Have Gone Before" and was based on Diane Duane's book, The Wounded Sky. Duane and Michael Reaves pitched the idea to David Gerrold and Gene Roddenberry, and then submitted a script. Their script was subsequently rewritten by Maurice Hurley, whose first effort was poorly received; however, he subsequently rewrote it and that version was filmed. The episode was the first of the series directed by Rob Bowman, who went on to direct 12 more episodes. It was the only Star Trek: The Next Generation assignment for writers Duane and Reaves.

Set in the 24th century, the series follows the adventures of the Starfleet crew of the Federation starship Enterprise-D. In "Where No One Has Gone Before", the Enterprise is visited by Mr. Kosinski (Stanley Kamel) and an alien known as the Traveler (Eric Menyuk). The Traveler sends the Enterprise to distant parts of the universe, and help is required from Wesley Crusher (Wil Wheaton) to bring the ship back home.

In this episode, Menyuk made the first of three appearances as the Traveler. Biff Yeager made his first appearance as the longest-running chief engineer of the first season.

The Enterprise rendezvous with the USS Fearless to bring aboard Mr. Kosinski (Kamel), a Starfleet propulsion expert who plans to run tests on the warp engines to improve their efficiency. Commander Riker (Jonathan Frakes) is skeptical of Kosinski's seemingly nonsensical specifications, suggesting his apparent success on other ships was merely addressing inherent design flaws on older engines, whereas the Enterprise's engines are brand new.

Kosinski arrives with his assistant, an alien from Tau Alpha C who claims his name is unpronouncable and asks them to refer to him as Kosinski's Assistant. As Kosinski and the Assistant explain the tests to the engineering crew, Wesley Crusher (Wheaton) quickly grasps what the tests are designed to accomplish and the Assistant expresses admiration for his problem-solving abilities.

The test quickly goes awry when the Enterprise speeds up, surpassing the known capabilities of warp engines. Jean-Luc Picard (Patrick Stewart) orders the ship stopped, and the crew finds themselves on the far side of the M33 Galaxy (more than 2.7 million light-years from the Milky Way, the Enterprise's home galaxy). Although Kosinski is pleased with the results, Picard reprimands him and asks him to simply redo the process to return home.

Crusher attempts to warn Riker that during the warp test, the Assistant appeared to "phase", drifting in and out of reality, but Riker dismisses him without listening. However, after Kosinski begins the second test, Crusher and Riker both observe the Assistant again drifting out, appearing more tired. The Enterprise again experiences a burst of speed, and when it stops, the crew cannot determine their position. Picard demands that Kosinski get the crew home.

While Kosinski, the Assistant, and the engineering crew work on reversing the process, the rest of the crew begins experiencing lifelike visions of their past. After having a vision of his mother (Herta Ware), Picard surmises that they have arrived at the theoretical Outer Rim of the universe, and issues a red alert to awaken the crew from their visions.

Riker suggests that Kosinski may have had nothing to do with the warp jumps, which were more likely done by the Assistant himself, resulting in his weakness. Picard finds the alien in sick bay, dying, but Dr. Crusher (Gates McFadden) cannot evaluate the Assistant's alien biology, and is unable to treat him.

The Assistant explains he is a Traveler with the ability to channel thought into reality, brought the crew of the Enterprise to the Outer Rim, triggering similar effects in anyone within it to ascertain if they were ready to experience thought as reality, and apologizes for bringing them before they were ready. The Traveler confides to Picard that he looks for scientific prodigies such as the young Crusher, and suggests that Picard nurture him.

When he returns to the engineering section, the Traveler asks Crusher to assist him in returning the Enterprise to known space. As they concentrate, beginning to return the ship home, the Traveler again phases and finally disappears completely. The Enterprise is back in Federation space. After the incident, Picard promotes Crusher to acting ensign (following his own unspoken suggestion in "The Naked Now") on the Enterprise for his performance.

The original story for "Where No One Has Gone Before" was developed before the start of Star Trek: The Next Generation, with Michael Reaves and Diane Duane invited to pitch story ideas. Duane did not belong to the Writers Guild of America (a requirement to write for the show at the time), and doubted she would be asked to write a script. Duane and Reaves worked together on several ideas, and after a week, Reaves informed Duane that he developed an idea based on her 1983 Star Trek novel The Wounded Sky and asked her to collaborate with him. She worked on the story idea with Reaves, and they expanded the story slightly from Reaves' original idea. One version of the script involved the Enterprise causing the birth of a new universe, with a play on the Genesis creation narrative.

They pitched the story to story editor David Gerrold, who brought them to Star Trek creator Gene Roddenberry. Gene favored the story idea, suggesting changes, which Reaves and Duane incorporated into a second draft. The episode was now entitled "Where None Have Gone Before", differing significantly from the final version: Kosinski was a roommate of Picard's at Starfleet Academy, and instead of the Traveler, the ship's extreme propulsion was provided by a "warpdrive booster" with a miniature black hole. The resolution of the plot involved imagining a duplicate miniature Enterprise and the interaction between the black holes on the two ships' propulsion units. After Duane and Reaves turned in the first version of the script based on that premise, nothing was heard from the TNG staff for two weeks.

The script was given to Maurice Hurley to rewrite. He took six weeks for the rewrite, and his initial version was received poorly by TNG executives. Hurley later said, "they absolutely hated it, I think they wanted to fire me, and they would have if I didn't have a guaranteed contract". He rewrote the script, and this version was filmed. Hurley was pleased with the result, saying that "everything about that episode worked". The final version differed significantly from the original Reaves-Duane script. Duane later said that only two scenes remained: where Picard sees his mother, and where he nearly falls out of the turbolift into space. Reaves later said that the episode "came together much better on the screen than we thought it would when we read the script. We were lucky, because it was out of our hands".

Donald Petrie was originally signed to direct the episode, but dropped out to direct the film Mystic Pizza. Executive producer Robert Justman brought in Rob Bowman to direct his first Star Trek episode. Justman later said that this was one of his most significant achievements on The Next Generation. Bowman worked on storyboards and set blocking for 20 days before shooting the episode. He was initially nervous about working on the show, and felt he had to prove himself because of his relative inexperience as a director. Bowman said that after the second day of filming, it became easier, and credited the crew with making him feel welcome. He went on to direct twelve more episodes of The Next Generation.

Eric Menyuk was cast as the Traveler. The actor had previously been runner-up for the role of Data several weeks earlier (the role went to Brent Spiner). He was a Star Trek fan since age six, and would later return as the Traveler twice more: in "Remember Me" and "Journey's End". Menyuk's return in "Journey's End" would also mark the last on-screen appearance of Wesley Crusher. Biff Yeager made his Next Generation debut in "Where No One Has Gone Before" as Chief Engineer Argyle, who would become the most frequently appearing chief engineer of the first season (appearing twice). Geordi La Forge took over that role in the first episode of season two, "The Child". Stuntman "Dangerous" Dennis Madalone also made his series debut as the science division crewman threatened by his own (imagined) fire. From season three onwards he was stunt coordinator for The Next Generation, and continued to portray a number of crew members. Viewers learned Picard's mother's first name in "Chain of Command"; she was played in "Where No One Has Gone Before" by Herta Ware, who appeared in the 1985 science-fiction film Cocoon.

Some effects in the episode were created in Robert Legato's basement with water reflections and Christmas tree lights. The script was vague about what was seen at the end of the universe, so Legato played with the effects of water reflections on his basement wall. Shooting through BoPET film, he created multiple images that were layered over one another for the final effect (which Legato described as "peculiar and bizarre"). Christmas tree lights were suspended and moved, to create the blinking effect seen on screen.

The Klingon Targ was created by dressing a tamed wild boar (named Emmy Lou) in an outfit created by costume designer William Ware Theiss. Executive producer Robert Justman later recalled, "That pig smelled horrid. A sweet-sour, extremely pungent odor. I showered and showered, and it took me a week to get rid of it!" To appear as the Traveler, Eric Menyuk wore a prosthetic piece (created by Michael Westmore) on his forehead, which ran into his hairline. He also wore a pair of false three-fingered hands, which were sold in the "It's A Wrap!" auction after the end of Star Trek: Enterprise. His Traveler costume was also sold at the auction.

"Where No One Has Gone Before" was the second episode scored by Ron Jones. Some themes in the soundtrack were rearrangements of Jerry Goldsmith's score from Star Trek: The Motion Picture. In the piece "Talk with Mom" (played during Picard's meeting with his mother), Jones tried to create an effect identical to the finale of Aaron Copland's 1944 Appalachian Spring. Alexander Courage's themes from The Original Series are included in a seven-note ostinato in the pieces "Log", "Visitors", and "Fly-By".

The score was recorded with a 40-piece orchestra. Jones formatted the orchestra to generate a bigger sound than normally heard on television soundtracks to make it sound more like Goldsmith's The Motion Picture score. Keyboards were used to make the cellos more prominent, and other changes included an increase in the midrange of the string section. The soundtrack to "Where No One Has Gone Before" was released (as part of The Ron Jones Project box set of Star Trek: The Next Generation scores) in a limited run of 5,000 copies in 2010 by Film Score Monthly.

"Where No One Has Gone Before" aired in broadcast syndication during the week commencing October 24, 1987. It received a Nielsen rating of 10.5, reflecting the percentage of all households watching the episode during its timeslot. This was the highest rating received by the series since "The Naked Now" three episodes earlier.

Several reviewers revisited the episode after the end of the series. Cast member Wil Wheaton later described the episode as "the first time The Next Generation really started to come together". However, the episode was flawed in dialogue and in Picard's changes in tone: "I'm not sure if that was a deliberate choice, so he would appear as a conflicted man, or if it was Patrick Stewart's natural warmth and kindness coming through the gruff demeanour Picard was written to have." When reviewing the show in 2006 for AOL TV, he gave it an overall score of B-plus. Keith DeCandido reviewed the episode for Tor.com, praising the guest actors: Stanley Kamel was "magnificent" and "ooze[d] arrogance, overconfidence, and bull in equal measure", while Herta Ware brought "tremendous gravitas" to her role. He described the episode as the best of the first season, with strong performances from the main cast, and gave it an overall score of eight (out of ten).

Jamahl Epsicokhan, on his website Jammer's Reviews, said that it was the first time in the series that space itself generated "awe and wonder"; however, he thought the "fresh and intriguing" nature of the episode faded as it went along. He criticized Wesley Crusher, describing him as a "cloying geek" and "you just want to strangle him". He gave the episode a score of 2.5 (out of 4).

In Richard Hanley's book The Metaphysics of Star Trek the appearance of the Traveler in "Where No One Has Gone Before" was described as a continuation of intellectually advanced aliens in Star Trek, beginning in The Original Series with Apollo in "Who Mourns for Adonais?" and Gary Mitchell in "Where No Man Has Gone Before". Metaphysics is referenced in this episode by Wesley Crusher, who asks if thought is the basis of existence.

The first home-media release of "Where No One Has Gone Before" was on VHS cassette on April 1, 1992 in the United States and Canada. The episode was later included on the Star Trek: The Next Generation season-one DVD box set released in March 2002.

Episodes from "Encounter at Farpoint" to "Datalore" were released in Japan on LaserDisc on June 10, 1995, as part of First Season Part.1. This included the first season episode "Where No One Has Gone Before", and the set has a total runtime of 638 minutes across multiple 12-inch optical video discs.

The episode was released as part of the season-one Blu-ray set on July 24, 2012. To celebrate the 25th anniversary of Star Trek: The Next Generation and promote the release of the first season on Blu-ray, the episodes "Where No One Has Gone Before" and "Datalore" received a theatrical release in the United States on July 23, 2012 in nearly 500 theaters. "Where No One Has Gone Before" was chosen by Star Trek experts Mike and Denise Okuda because of the unusual space special effects.

• "Where No One Has Gone Before" at IMDb
• "Where No One Has Gone Before" at Memory Alpha