The Time line of the British Army 1900–1999 lists the conflicts and wars the British Army were involved in.

• Boxer Rebellion ended 1901
• Anglo-Aro War 1901–1902
• Second Boer War ended 1902
• World War I 1914–1918
• Easter Rising 1916
• Third Afghan War 1919
• Irish War of Independence 1919–1921
• World War II 1939–1945
• Greek civil war 1946-47
• Malayan Emergency 1948–1960
• Korean War 1950–1953
• Mau Mau Uprising 1952–1960
• Cypriot Independence 1955–1959
• Suez Crisis 1956–1957
• Brunei Revolt 1962–1966
• Indonesia–Malaysia confrontation 1962-1966
• Dhofar Rebellion 1962–1975
• Aden Emergency 1963–1967
• The Troubles 1968–1998
• Operation Banner 1969–2007
• Falklands War 1982
• Gulf War 1990–1991
• Yugoslav wars 1991–2001
• Bosnian War 1992–1995
• Kosovo War 1998–1999

• Timeline of the British Army
• Timeline of the British Army 1700–1799
• Timeline of the British Army 1800–1899
• Timeline of the British Army since 2000