Kingdom of Siam may refer to:

  • Sukhothai Kingdom (1238–1351)
  • Ayutthaya Kingdom (1351–1767)
  • Thonburi Kingdom (1768–1782)
  • Rattanakosin Kingdom (1782–1932)
  • Thailand before 24 June 1939 and again from 8 September 1945 to 20 July 1949