Heathrow Terminal 4 is an airport terminal at Heathrow Airport, the main airport serving London, England, situated to the south of the southern runway, next to the cargo terminal. It is connected to Heathrow Terminals 2 and 3 by the vehicular Heathrow Cargo Tunnel, and by rail with the Heathrow Terminal 4 tube and Heathrow Terminal 4 railway stations.
The Prince and Princess of Wales opened Terminal 4 on 1 April 1986. British Airways was the main airline operating from the terminal from 1986 until its move to Terminal 5 on 29 October 2009, eventually making Terminal 4 the Heathrow base for airlines of the SkyTeam airline alliance.