He was elected Friday during a special parliamentary session after his predecessor Anerood Jugnauth resigned in March following open conflict with Prime Minister Navin Chandra Ramgoolam.
The row erupted when the leader of the opposition in parliament, Paul Berenger, announced the creation of a new opposition alliance headed by Jugnauth.
Ramgoolam himself asked Jugnauth to either deny the statement by the opposition, or, in the case of confirmation, to resign, arguing his new role was incompatible with a position as head of state.
Vice President Monique Ohsan Bellepeau filled in until Purryag, 64, the former president of the National Assembly, was sworn in Saturday in the presence of both Ramgoolam and Berenger.
Purryag and Ramgoolam are both members of the Labour Party.
An attorney by training, Purryag has worked in politics for 36 years, holding several ministerial positions as well as acting as deputy prime minister. He became speaker of parliament in 2005.
Mauritius is an archipelago of four islands in the Indian Ocean that gained independence from Britain in 1968.
It has since been considered a stable democracy and has sustained economic growth to make its 1.2 million inhabitants among the richest in Africa.
Best known for its top-end tourism and as a honeymoon destination, Mauritius recently made headlines after a honeymooner from Northern Ireland was strangled in January 2011 in her luxury hotel room. – AFP