400 (disambiguation)

400 may refer to:


 * 400 (number), the natural number following 399 and preceding 401
 * A year: 400 BC or AD 400
 * The Four Hundred, the oligarchic government controlling Athens after the Athenian coup of 411 BC
 * The Four Hundred (1892), the social elite of New York City in the late 19th century
 * The Four Hundred (band), an American indie rock band
 * The Game's Four Hundred, the subtitle of the almanac, the Baseball Register
 * List of highways numbered 400
 * Twin Cities 400, a passenger train operated by Chicago & Northwestern Railway from 1935 to 1963
 * 400 (card game), a Lebanese trick-taking game
 * HTTP 400, the HTTP error code for "Bad Request"
 * Ping Shan stop, Hong Kong; station code