Cozumel (Spanish pronunciation: [kosuˈmel]; Yucatec Maya: Kùutsmil) is an island and municipality in the Caribbean Sea off the eastern coast of Mexico's Yucatán Peninsula, opposite Playa del Carmen. It is separated from the mainland by the Cozumel Channel and is close to the Yucatán Channel. The municipality is part of the state of Quintana Roo, Mexico.

The name Cozumel was derived from the Mayan "Cuzamil" (also spelled "Cutzmil") or "Ah Cuzamil Peten" in full, which means "the island of swallows" (Spanish: Isla de las Golondrinas).

The island is located in the Caribbean Sea along the eastern side of the Yucatan Peninsula about 82 km (51 mi) south of Cancún and 19 km (12 mi) from the mainland. The island is about 48 km (30 mi) long and 16 km (9.9 mi) wide, with a total area of 477.961 km (184.542 sq mi). It is Mexico's largest Caribbean island, largest permanently inhabited island, and Mexico's third-largest island, following Tiburón Island and Isla Ángel de la Guarda. The population of Cozumel is 88,626 (2020 census). The majority of the island's population lives in the town of San Miguel, which has a population of 84,915 (2020 census). Cozumel is a municipality which also includes two small areas on the mainland, the ecotourism park of Xel-Ha and the Calica limestone quarry. All combined, Cozumel has a total land area of 647.33 km (249.94 sq mi). Cozumel has 5 main piers. Punta Langosta, the International Pier (SSA), and Puerta Maya are all piers for cruise ships. A ferry pier in San Miguel is used for passenger ferries to and from Playa del Carmen, as well as for cruise ship tenders. A fifth pier south of downtown is used only for vehicle ferries.

Large parts of the island are covered with mangrove forest which has many endemic animal species. Cozumel is a flat island based on limestone, resulting in a karst topography. The highest natural point on the island is less than 15 m (49 ft) above sea level. The cenotes are water-filled sinkholes formed by water percolating through the soft limestone soil for thousands of years. Eighteen deep cenotes and more than 250 shallow bodies exist on the island. Many are under dense vegetation. Jade Cavern Cozumel (Cenote Chempita) near El Cedral is often visited by tourists.

Endemic species and subspecies of bird include

• the Cozumel emerald
• the Cozumel great curassow, which is vulnerable
• the Cozumel thrasher, which is nearly, if not already, extinct
• the Cozumel vireo
• the Cozumel wren

Endemic dwarf mammals are found on the island include

• the Cozumel fox, which is nearly, if not already, extinct
• the Cozumel Island coati, which is endangered.
• the Cozumel Island raccoon, which is critically endangered

Three rodents of Cozumel are larger than their mainland counterparts: Oryzomys couesi, Peromyscus leucopus, and critically endangered Reithrodontomys spectabilis, the latter of which is also endemic to the island.

Endemic marine life includes

• the splendid toadfish

Other native wildlife includes

• the American crocodile
• the black spiny-tailed iguana
• the blue land crab (Cardisoma guanhumi)

Invasive species include

• the boa constrictor

The Cozumel flag displays a swallow on a blue and white background. The blue background represents the sea, while the white represents the purity of the Mayans. The sun represents the position of the island in the eastern region of the country, and the swallow indicates the meaning of the word Cozumel in the Mayan language. The sword is Spanish and represents the conquest of the island by the Spaniards in 1521.

Cozumel is surrounded by a diverse ecosystem of coral reefs that is home to more than 1,000 marine species. The reefs are primarily found on underwater cliffs; some exist in coastal lagoons and on sand bars at the north tip of the island. These reefs are part of the much larger Mesoamerican Barrier Reef System, which is the second largest reef in the world, stretching over 1,000 kilometers (620 mi). Cozumel's deeper coral reefs were historically famed for their black corals, yet black coral populations declined from the 1960s to the mid-1990s because of overharvesting and by 2016 had not recovered. A large portion of the reef on the south side of the island is sectioned off into the Arrecifes de Cozumel National Park. This park is protected under the Ramsar Convention along with Manglares y Humedales del Norte de Isla Cozumel; they both are included in the UNESCO protected area called Isla Cozumel Biosphere Reserve, Mexico. The reefs in Cozumel are made up of hard coral and soft coral. The marine life that inhabit the reefs include zoanthids, polychaetes, actinarians, hydroids, sponges, crustaceans, mollusks, echinoderms, and many varieties of Caribbean fish. The park is also a habitat to several endangered marine species such as the loggerhead sea turtle, hawksbill sea turtle, queen triggerfish, and the endemic splendid toadfish. Due to the abundant marine life and coral reefs, as well as the clear and warm Caribbean water, Cozumel is considered one of the best scuba-diving destinations in the world.

Scuba diving is one of Cozumel's primary attractions, mainly due to the coral reef on the western shore of Cozumel. These coral reefs are protected from the open ocean by the island's natural geography. In 1996, the government of Mexico also established the Cozumel Reefs National Marine Park, forbidding anyone from touching or removing any marine life within the park boundaries. Despite the importance of healthy reefs to Cozumel's tourist trade, a deepwater pier was built in the 1990s for cruise ships to dock, causing damage to the reefs, and it is now a regular stop on cruises in the Caribbean. Over the past few decades, coral reef health has significantly declined in Cozumel, with much lower coral cover now present than was historically recorded.

In September 2019, the Marine Park of Cozumel began to close reefs periodically for rehabilitation. They currently close a different reef every two months and the reefs are responding positively.

Cozumel has a tropical savanna climate under the Köppen climate classification that closely borders on a tropical monsoon climate. The dry season is short, from February to April, but even in these months precipitation averages about 45 millimeters (1.8 in) of rain per month. The wet season is lengthy, covering most of the months, with September and October being the wettest, when precipitation averages over 240 millimeters (9.4 in). Thunderstorms can occasionally occur during the wet season. Temperatures tend to remain stable with little variation from month to month, though the temperatures are cooler from December to February. The coolest month, January, averages 22.9 °C (73.2 °F). Owing to its proximity to the sea, the island is fairly humid, with an average humidity of 83%. The wettest recorded month was October 1980, with 792 millimeters (31.2 in) of precipitation and the wettest recorded day was June 19, 1975, with 281 millimeters (11.1 in). Extremes range from 9.2 °C (48.6 °F)—recorded January 18, 1977—to 39.2 °C (102.6 °F).

The Maya are believed to have first settled Cozumel by the early part of the 1st millennium AD, and older Preclassic Olmec artifacts have been found on the island as well. The island was sacred to Ixchel, the Maya Moon Goddess of fertility.

In the Mayan culture, all women were required to travel to the island at least once to worship Ixchel. She was the wife of Itzamna, the supreme Mayan lord of the skies of the night and of the day. The women asked Ixchel for fertility and for a joyful motherhood. Archeologists continue to unearth small dolls once sacrificed in the fertility rituals.

A number of ruins can be found on the island, most from the Post-Classic period. The largest Maya ruins on the island were near the downtown area and have now been destroyed. Today, the largest remaining ruins are at San Gervasio, located approximately at the center of the island.

The first Spanish expedition to visit Cozumel was led by Juan de Grijalva in 1518. In the following year, Hernán Cortés stopped by the island on his way to Veracruz. The Grijalva and Cortés expeditions were both received peacefully by the Maya of Cozumel (unlike their experiences on other parts of the mainland). Even after Cortés destroyed some of the Maya idols on Cozumel and replaced them with an image of the Virgin Mary, the native inhabitants of the island continued to help the Spanish re-supply their ships with food and water so they could continue their voyages. Gerónimo de Aguilar, a captive of the Mayans, was rescued at this time.

As many as 10,000 Maya lived on the island in the early 1500s, but in 1520, infected crew members of the Pánfilo de Narváez expedition brought the smallpox contagion to the island, and by 1570, only 186 men and 172 women were left alive on Cozumel. In the ensuing years, Cozumel was often the target of attacks by pirates, and in 1650, many of the islanders were forcibly relocated to the mainland town of Xcan Boloná to avoid the buccaneers' predation. Later, in 1688, most of the rest of the island's population, as well as many of the settlements along the Quintana Roo coast, were evacuated inland to towns such as Chemax.

In 1848, refugees escaping the tumult of the Caste War of Yucatán settled on the island, and in 1849 the town of San Miguel de Cozumel was officially recognized by the Mexican government.

In 1861, American President Abraham Lincoln ordered his Secretary of State, William Henry Seward, to meet with the Mexican chargé d'affaires Matias Romero to explore the possibility of purchasing the island of Cozumel for the purpose of relocating freed American slaves offshore. The idea was summarily dismissed by Mexican President Benito Juarez, and Juarez is still revered by the people of Cozumel because of this action. In 1862, Lincoln did manage to establish a short-lived colony of ex-slaves on Île à Vache off the coast of Haiti.

Work on the original Cozumel airport began when the US needed a stopover to aid World War II planes. While it was able to handle jet aircraft and international flights, it was never a US military base. By 1944, it was only used for emergencies and by the Mexican military. Eventually, Transportes Aeros Mexicanos began using the airport for domestic flights. Cozumel International Airport was built in the late 1970s and expanded in 1999.

On December 18, 2000, 41-year-old British singer-songwriter Kirsty MacColl, died while holidaying there with her sons and her boyfriend musician, James Knight, when a powerboat fatally struck her.

The island was struck directly by two Category 4 hurricanes during the 2005 Atlantic hurricane season. In July, Hurricane Emily passed just south of Cozumel, exposing the island to the storm's intense inner core. It was the larger, stronger, slower-moving Hurricane Wilma that caused the most destruction when it hit the island in October. A category 5 hurricane with winds over 150 miles per hour, Wilma's eye passed directly over Cozumel.

The storm caused some damage to the underwater marine habitat. This included the coral reefs, which suffered particularly at the shallower dive sites, and the fish that inhabit the reefs.

Trees, power lines, and cell phone towers were blown down, cars over-turned, piers washed away, windows smashed, roads collapsed, and new rivers appeared.

The economy of Cozumel is based on tourism, including daily visits from cruise ship passengers, as well as tourists scuba diving, snorkeling, and charter fishing. Some controversy exists over the detrimental effects tourism has on the ecosystem of Cozumel.

In addition to restaurants, hotels, and dive shops, vendors near the ports sell a variety of souvenirs and jewelry. All of these contribute greatly to the economy of Cozumel.

Other water activities include para-sailing, kitesurfing, and a tourist submarine. There are also two dolphinariums. The only working pearl farm in the Caribbean is located on the north edge of the island.

San Miguel de Cozumel, the main town on the island, is home to many restaurants with a variety of cuisines, along with several discothèques, bars, cinemas, and outdoor stages. The main plaza is surrounded by shops; in the middle of the plaza is a fixed stage where Cozumeleños (people of Cozumel) and tourists celebrate every Sunday evening with music and dancing.

All food and manufactured supplies are shipped to the island. Water is provided by three different desalination facilities located on the island.

There are three universities on the island: the State Public University of Quintana Roo (UQROO) and two private universities, the Partenon Institute and the Interamerican University for Development (UNID). In addition to teaching English as a degree program, they offer other career options including natural resources research, tourism and commercial systems. The Cozumel Arts University offers artist education at the bachelor's level.

The Festival of Santa Cruz and El Cedral Fair is a historical tradition held in the town of El Cedral, in the south of Cozumel Island at the end of April. This annual event is said to have been started over 150 years ago by Casimiro Cárdenas. Cárdenas was one of a group that fled to the island from the village of Saban, on the mainland, after an attack during the Caste War of Yucatán in 1848. The attackers killed other villagers, but Cárdenas survived while clutching a small wooden cross.

• 
  El Cedral

Legend has it that Cárdenas vowed to start an annual festival wherever he settled, to honor the religious power of this crucifix. Today, the original Holy Cross (Santa Cruz) Festival forms part of the wider Festival of El Cedral, which includes fairs, traditional feasts, rodeos, bullfights, music and competitions. The celebrations last about five days in all and are held every year at the end of April or beginning of May.

The Cozumel Carnival or Carnaval de Cozumel is one of the most important carnival festivities in México. It has been celebrated as a tradition beginning from the late nineteenth century and fills Cozumel's streets with parades. It begins the week before Mardi-Gras in February. Cozumel's Carnival is a tradition which has been passed down through many generations that celebrates a mixture of cultures that escaped to the warm embrace of Cozumel. Dating back to the mid-1800s, Cozumel Carnaval was started by young people dressed in vibrantly colorful costumes known as "Estudiantinas" or "Comparsas", who expressed themselves in the streets of Cozumel through the artforms of dance, song, and fantasy.

Cozumel Municipality is one of eleven municipalities of Quintana Roo. The municipal seat is located in San Miguel de Cozumel, the largest city in the municipality.

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• Cozumel is one of the locations featured in the 2006 video game Tom Clancy's Splinter Cell: Double Agent.
• Cozumel and its Mayan ruins are featured in the program I Shouldn't Be Alive Season 6, Episode 5: "Lost In The Jungle".
• Cozumel is one of the locations featured in the 2018 video game Shadow of the Tomb Raider.
• Cozumel is featured as one of the primary settings and filming locations of the 1984 film, Against All Odds.

• Cozumel Port