Simon Jonathan Sebag Montefiore, born 27 June 1965, is a British historian, television presenter and author of popular history books and novels. Simon Sebag Montefiore was born in London. His father was psychotherapist Stephen Eric Sebag Montefiore (1926–2014), a great-grandson of the banker Sir Joseph Sebag-Montefiore (1822-1903), the nephew and heir of the wealthy philanthropist Sir Moses Montefiore[3] considered by some "the most important Jew of the 19th century". Simon's mother was Phyllis April Jaffé, (1927–2019) from the Lithuanian branch of the Jaffe family. Her parents fled the Russian Empire at the beginning of the 20th century. They bought tickets for New York City, but were cheated, being instead dropped off at Cork, Ireland. Due to the Limerick boycott in 1904 her father Henry Jaffé left the country and moved to Newcastle upon Tyne, England.[4] Simon's brother is Hugh Sebag-Montefiore.

The Montefiore family are descended from a line of wealthy Sephardi Jews who were diplomats and bankers all over Europe and who originated from Morocco and Italy. After the Alhambra Decree was issued against the Jews in Spain of 1492, some of Montefiore's ancestors stayed in the country whilst remaining secretly Jewish. During the reign of Philip II of Spain, one of them became governor of a province of Mexico, where he and his family were denounced by a political rival and tortured by the Inquisition. Two teenaged girls were burned alive in Mexico City while a son escaped to Italy and changed his name to Montefiore.

Sebag Montefiore was educated at Ludgrove School and Harrow School where he was editor of the school newspaper, The Harrovian. In the autumn of 1983 he interviewed Margaret Thatcher for The Harrovian.He won an Exhibition to read history at Gonville and Caius College, Cambridge where he received his Doctorate of Philosophy (PhD).