Sir Mark Thatcher, 2nd Baronet (born 15 August 1953) is a British businessman.
He is the son of Margaret Thatcher, former Prime Minister of the United Kingdom, and Sir Denis Thatcher, and is the twin brother of Carol Thatcher.
His early career in business frequently led to questions being raised that he was benefiting from his mother's position, notably in relation to the Al-Yamamah arms deal.
He left the UK in 1986, and has since lived in the United States, Switzerland, Monaco, South Africa, Gibraltar, Barbados, Guernsey, and Spain.
In 2004 the Sunday Times estimated his wealth at £60 million, most of which they suggested was in offshore accounts.
He has two children by his first wife, Diane Burgdorf.
He married his second wife, Sarah Jane Russell, in 2008.
After his father's passing in 2003, he became Sir Mark Thatcher and succeeded to the Thatcher baronetcy, a hereditary title which had unusually been given to his father in 1990 (this being the only baronetcy created since 1964).