Philip Nicholas Seton Mansergh OBE (27 June 1910 – 16 January 1991) was a historian. His focus was on Ireland and the British Commonwealth. He was Master of St John's College, Cambridge (1969-1979). He was chair of British Commonwealth relations at Chatham House (1945-1953). Then in 1953 the Smuts Professor of Commonwealth History at Cambridge University, where he trained many of the specialists in the field of Irish, Indian, and Commonwealth studies. He played the central role in assembling and editing the "monumental" 12-volume edition of historical documents associated with the independence of India.[1]