General Mohamed Ould Abdelaziz came to power by ousting his democratically-elected predecessor, President Sidi Ould Cheikh Abdallahi, in a military coup in August 2008.
Nearly a year later, he won his own democratic mandate by being elected president in elections held under an agreement with coup opponents in July 2009.
The official results gave Gen Abdelaziz 52%, well ahead of the second placed candidate, parliament speaker Messaoud Ould Boulkheir, who got 16%.
The main opposition candidates claimed the result was fabricated and merely designed to legitimise Gen Abdelaziz's military rule, but international observers said the vote had been largely free and fair. Sid'Ahmed Ould Deye, the head of the Electoral Commission, resigned after expressing his own doubts about the result.
In 2013, Gen Abdelaziz's Union for the Republic party won a majority in parliament, in elections that had been repeatedly delayed as a result of opposition doubts about fairness.
All but one member of the main opposition alliance refused to take part in the vote, describing it as a "farce".
Previously serving as President Abdallahi's chief of the presidential staff, he toppled his boss when Mr Abdallahi tried to dismiss him in August 2008, amid reports of a political rift between the two men.
Gen Abdelaziz had also been instrumental in the 2005 coup that overthrew former President Maaouiya Ould Taya and installed the coup leader Ely Ould Mohamed Vall as president.
President Abdallahi's overthrow was one of 11 coups or attempted coups since independence from France in 1960. He won a presidential vote in March 2007 to become Mauritania's first democratically-elected president since independence.
The European Union early in 2010 decided to resume full cooperation with Mauritania following a restoration of constitutional rule.
President Abdelaziz was treated in France in October-November 2012 after he was shot in the arm in what officials say was a mistaken military attack on his convoy.