Sir Martin John Gilbert, CBE, D.Litt. (born October 25, 1936) is a British historian and the author of over eighty books, including works on the Holocaust and Jewish history. He has been a pioneer of historical atlases, and is best known as the official biographer of Sir Winston Churchill.

Martin Gilbert was born in London to Peter and Miriam Gilbert. Nine months after the outbreak of World War II, he was evacuated to Canada as part of the British efforts to safeguard children. Vivid memories of the transatlantic crossing from Liverpool to Quebec sparked his curiosity about the war in later years. After the war he attended Highgate School, and then completed two years of National Service before going on to study modern history at Magdalen College, Oxford, graduating in 1960 with a BA. One of his tutors at Oxford was A.J.P. Taylor. After his graduation, Gilbert undertook postgraduate research at St Antony's College, Oxford. In 1963, he married Helen Constance Robinson, with whom he had a daughter. He had two sons with his second wife, Susan Sacher. Since 2005, he has been married to the Holocaust historian Esther Gilbert, née Goldberg.

After two years of postgraduate work, he was approached by Randolph Churchill for help in writing a biography of his father, Sir Winston Churchill. That same year, 1962, he was made a Fellow of Merton College, Oxford, and he spent the next few years combining his own research projects in Oxford with being part of Randolph's research team in Suffolk, working on the first two volumes of the Churchill biography. When Randolph died in 1968, Gilbert was commissioned to take over the task, completing the final six main volumes of the biography. Gilbert spent twenty years on the six narrative volumes, releasing a number of other books throughout the time. Each main volume of the biography is accompanied by two or three volumes of documents, and so the biography currently runs to 24 volumes (over 25,000 pages), with another 7 document volumes still planned.