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, 1st Baronet, and is the twin brother of Carol Thatcher. He has two children by his first wife, Diane Burgdorf. He married his second wife, Sarah Jane Russell, daughter of Terence (Terry) J. Clemence, a wealthy property developer, and sister of Viscountess Rothermere, in 2008.
On the death of his father in 2003 he became Sir Mark Thatcher when he 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).His early career in business frequently led to questions being raised that he was benefiting from his mothers position, notably in relation to the Al-Yamamah arms deal. In 2004 the Sunday Times estimated his wealth at £60 million, most of which they suggested was in offshore accounts.
In 2005 he was convicted and given a four-year suspended jail sentence and a fine in South Africa in relation to the 2004 Equatorial Guinea coup détat attempt. He left the UK in 1986, and since then has lived in the United States, Switzerland, Monaco, South Africa and more recently in Gibraltar, Barbados, Guernsey, and Spain.