Former Health minister Maithripala Sirisena walked out of the Mahinda Rajapaksa's government a day after polls were called. It set off a wave of political turmoil and energised a long-dispirited opposition that had not been looking forward to the election.
The 63 year old lead a potentially fractious coalition of ethnic, religious, Marxist and centre-right parties in the elections.
Sirisena was mainly backed by the centre-right United National Party (UNP). Sirisena has said that his prime minister will be UNP leader Ranil Wickremesinghe.
Former president Chandrika Kumaratunga came out of retirement to urge her supporters to back Sirisena. This prompted the Rajapaksa government to claim he was being used as Kumaratunga's proxy.
Sirisena has said he will bring in constitutional and democratic reforms to weaken the power of the presidency. He has pledged to abolish the executive presidency that gave Rajapaksa unprecedented power and hold a fresh parliamentary election within 100 days.
He has also vowed to root out corruption, promising a crackdown on corruption, which would include investigations into big infrastructure projects such as a $1.5 billion deal with China Communications Construction Co Ltd to build a port city.
Before the elections, Sirisena had said that in the interest of national security he would not withdraw troops from northern Sri Lanka which is a Tamil dominated region.
Sirisena won his first parliamentary election in 1989 from the district of Polonnaruwa.
At the age of 20, Sirisena was suspected of leading an anti-government revolt and was arrested. He spent two years in jail.
He was a target of LTTE rebels during the separatist war. In 2008, an LTTE suicide bomber attacked a convoy Sirisena was part of.
