Simon's father, a doctor, is descended from a famous line of wealthy Sephardic Jews who became diplomats and bankers all over Europe. At the start of the 19th century, by playing the markets based on intelligence about the Battle of Waterloo, Simon's great-great uncle, Sir Moses Montefiore, became a banking partner of N M Rothschild & Sons. By contrast, Simon’s mother, April, a novelist, comes from a Lithuanian Jewish family of poor scholars. (Simon is related to Gwyneth Paltrow through his great-grandmother, a Paltrovitch.) Her parents fled the Russian Empire at the turn of the 20th century. They bought tickets for New York City but were cheated and dropped off at Cork, Ireland. In Ireland, they survived the 1904 Limerick pogrom and fled again, to Newcastle, England.

Simon was educated at Ludgrove School, Harrow, and Gonville and Caius College, Cambridge, where he read history.

Montefiore’s books are world bestsellers, published in 33 languages. His first history book, Catherine the Great & Potemkin, was shortlisted for the Samuel Johnson, Duff Cooper, and Marsh Biography Prizes. Stalin: The Court of the Red Tsar won History Book of the Year at the 2004 British Book Awards. Young Stalin won the LA Times Book Prize for Best Biography, the Costa Book Award, the Bruno Kreisky Award for Political Literature, the Prix de la Biographie Politique and has been shortlisted for the James Tait Black Memorial Prize.

Miramax Films and Ruby Films have bought the rights and are currently developing a movie of Young Stalin.

He also wrote a novel, Sashenka, and his next history book is Jerusalem: the Biography, a fresh history of the Middle East.

A Fellow of the Royal Society of Literature, he lives in London with his wife and sister-in-law, the novelist Santa Montefiore, and their two children. His father-in-law is the Anglo-Argentine landowner Charles Palmer-Tomkinson, his brother is Hugh Sebag-Montefiore and his sister-in-law is the socialite Tara Palmer-Tomkinson. His friends include Prince Charles and British prime minister David Cameron.

Non Fiction

• Jerusalem: the Biography, a fresh history of the Middle East, ...
• 101 World Heroes, 2009
• Monsters — History's most evil men and women, 2008
• Young Stalin, 2008
• Stalin: The Court of the Red Tsar, 2005, 2004 ISBN 1400042305 ISBN 978-1400042302
• Potemkin: Catherine the Great's Imperial Partner, 2005Catherine the Great and Potemkin, 2004
• Speeches that Changed the World: The Stories and Transcripts of the Moments that Made History, 2008, 2007Speeches that Changed the World, 2007
• Piggy Foxy and the Sword of Revolution: Bolshevik Self-Portraits (Annals of Communism Series) with Alexander Vatlin, Larisa Malashenko and Vadim A. Staklo, 2006
• A History of Caucasus, 2005 ISBN 0297819259 ISBN 978-0297819257
• King's Parade, 1992

Fiction

• Sashenka, 2008
• My Affair with Stalin, 2004