Orlando (/ɔːrˈlændoʊ/ ^ⓘ or-LAN-doh) is a city in and the county seat of Orange County, Florida, United States. Part of Central Florida, it is the fourth-most populous city in the state and its most populous inland city, with a population of 307,573 at the 2020 census. The Orlando metropolitan area, with over 2.94 million residents, is the third-largest metropolitan area in Florida and 20th-largest in the United States.

Orlando is one of the most-visited cities in the world primarily due to tourism, major events, theme parks, and convention traffic. It is the fourth-most visited city in the U.S. after New York City, Miami, and Los Angeles, with over 3.5 million visitors as of 2023. Orlando International Airport is the 7th-busiest airport in the United States and the 18th-busiest in the world. The two largest and most internationally renowned tourist attractions in the Orlando area are the Walt Disney World resort, opened by the Walt Disney Company in 1971 and located about 21 miles (34 km) southwest of Orlando in Bay Lake, and the Universal Orlando resort, opened in 1990 as a major expansion of Universal Studios Florida and the only theme park inside Orlando city limits.

Apart from its theme parks, most major cultural sites such as Orlando Museum of Art and Dr. Phillips Center for the Performing Arts, and nightlife, bars, and clubs are located in downtown Orlando. Other attractions like Orlando Eye at ICON Park are located along International Drive. The city is also one of the busiest American cities for conferences and conventions; Orange County Convention Center is the second-largest convention facility in the United States. Orlando is home to the University of Central Florida, one of the largest universities in the United States. The city's major league professional sports teams include Orlando City SC (MLS) and the Orlando Magic (NBA).

Fort Gatlin, as the Orlando area was once known, was established at what is now just south of the city limits by the 4th U.S. Artillery under the command of Lieutenant Colonel Alexander C. W. Fanning on November 9, 1838, during the construction of a series of fortified encampments across Florida during the Second Seminole War. The fort and surrounding area were named for John S. Gatlin, an Army physician who was killed in Dade's Massacre on December 28, 1835. The site of construction for Fort Gatlin, a defensible position with fresh water between three small lakes, was likely chosen because the location was on a main trail and is less than 250 yards from a nearby Council Oak tree, where Native Americans had traditionally met. King Phillip and Coacoochee frequented this area and the tree was alleged to be the place where the previous 1835 ambush that had killed over 100 soldiers had been planned. When the U.S. military abandoned the fort in 1839, the surrounding community was built up by settlers.

Prior to being known by its current name, Orlando was once known as Jernigan. This name originates from the first European permanent settlers, Isaac and Aaron Jernigan, cattlemen who moved from the state of Georgia and acquired land 2 miles (3.2 km) northwest of Fort Gatlin along the west end of Lake Holden in July 1843 by the terms of the Armed Occupation Act. Aaron Jernigan became Orange County's first state representative in 1845, but his pleas for additional military protection went unanswered.

Fort Gatlin was briefly reoccupied by the military for a few weeks during October and November 1849, and subsequently a volunteer militia was left to defend the settlement. A historical marker indicates that by 1850, the Jernigan homestead (or Fort Gatlin in some sources) served as the nucleus of a village named Jernigan. According to an account written years later by his daughter, at that time, about 80 settlers were forced to shelter for about a year in "a stockade that Aaron Jernigan built on the north side of Lake Conway". One of the county's first records, a grand jury's report, mentions a stockade where it states homesteaders were "driven from their homes and forced to huddle together in hasty defences [sic]." In 1852, Aaron Jernigan led a local volunteer militia beginning in advance of the Third Seminole War.

A post office opened at Jernigan in 1850. Jernigan appears on an 1855 map of Florida, and by 1856, the area had become the county seat of Orange County. In 1857, the post office was removed from Jernigan, and opened under the name of Orlando at a new location in present-day downtown Orlando. The move is believed to have been sparked, in part, by Aaron Jernigan's fall from grace after he was relieved of his militia command by military officials in 1856. His behavior was so notorious that United States Secretary of War Jefferson Davis wrote, "It is said they [Jernigan's militia] are more dreadful than the Indians." In 1859, Jernigan and his sons were accused of committing a murder at the town's post office. They were then transported to Ocala, but escaped. During the American Civil War, the post office closed, but reopened in 1866.

At a meeting in 1857, debate had grown concerning the name of the town. Pioneer William B. Hull recalled how James Speer (a local resident, and prominent figure in the stories behind the naming of Orlando) rose in the heat of the argument and said, "This place is often spoken of as 'Orlando's Grave.' Let's drop the word 'grave' and let the county seat be Orlando."