Treaty of Westminster may refer to:

• Treaty of Westminster (1153), also known as the Treaty of Wallingford
• Treaty of Westminster (1462), also known as the Treaty of Westminster-Ardtornish
• Treaty of Westminster (1511), an alliance during the War of the League of Cambrai
• Treaty of Westminster (1527), an alliance during the War of the League of Cognac
• Treaty of Westminster (1654), ending the First Anglo-Dutch War
• Triple Alliance (1668), concluded in Westminster between Sweden, the General States and Great Britain
• Treaty of Westminster (1674), ending the Third Anglo-Dutch War
• Treaty of Westminster (1756), establishing neutrality between Great Britain and Prussia
• The Statute of Westminster 1931, which transformed the British Empire into the British Commonwealth of Nations, is sometimes referred to (particularly in the former dominions) as a "Treaty" of Westminster