Tran Dai Quang won 91.5 per cent of the votes during a ballot at the rubber stamp parliament early today, having been nominated by party officials for the largely ceremonial role during the five-yearly Communist Party Congress in January.
Vietnam is in the midst of a leadership handover, with communist leader Nguyen Phu Trong reelected in January as party secretary general in a victory for the party's old guard.
"I sincerely thank the National Assembly for electing me," Quang said as he was sworn in according to a media officer at the parliament, who spoke on condition of anonymity.
Authoritarian Vietnam is run by the Communist Party and officially led by a triumvirate of party secretary general, president, and prime minister, with key decisions being made by the 19-member politburo.
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Reformist Prime Minister Nguyen Tan Dung lost out in internal party elections and is due to step down next week, when the National Assembly will vote on his replacement.
In the past, the leadership handover was decided at the party congress but took up to six months to be confirmed by the National Assembly.
Analysts say this year things have moved more quickly, partly because several top leaders are retiring from politics, and also because of an upcoming visit by Obama in May.
Quang, 59 and a career policeman, rose the ranks within the country's Ministry of Public Security.
His election marks the first time a police general has been made president, said Le Hien Duc, 84, an anti-corruption activist.
Vietnam's Ministry of Public Security is a powerful body with sweeping powers including intelligence gathering and protecting the party from perceived threats, both domestic and overseas.