Bikini Bottom is the main setting in the SpongeBob SquarePants series. It is an undersea city-state where SpongeBob and his friends live. According to Nickelodeon's program summary, Bikini Bottom is located in the Pacific Ocean, beneath Bikini Atoll in the Marshall Islands.[2] The city's population fluctuates throughout the series. In "Nautical Novice," Mrs. Puff states that Bikini Bottom is home to millions of people. In "The Good Krabby Name" and "Yeti Krabs," Bikini Bottom is shown to have a population of about 500. The city has historically gone by the names of Bikini Bottomshire, Bikini Gulch, and temporarily, "Dead Eye Gulch."

The city is run by the mayor, and governed by the royal family, as they rule over the entire ocean.

It consists of several various different businesses, including restaurants, stores, and manufacturers. The city has a stable economy, a balanced education system, questionable healthcare, labor laws, a structured government, and a firm law-enforcement system. There are stadiums, amusement parks, and other recreational places such as Glove World! a recurring location in the series.

Bikini Bottom is home to almost all of the entire central cast of SpongeBob SquarePants.