By Candace Piette
BBC News, Montevideo
Jose Mujica celebrated his victory in the election
A former left-wing militant who spent almost 15 years in prison during the country's military rule appears to have won the presidential elections.
Reliable exit polls give Jose Mujica, 74, just over 50% of the vote in a run-off poll.
His main rival and former President Luis Alberto Lacalle has conceded.
Mr Mujica succeeds a popular head of state, Tabare Vazquez, who has been in power for the last five years as Uruguay's first left-wing president.
With his election victory, Mr Mujica has completed his transformation from left wing rebel to statesman.
A plain-speaking maverick, who lives a frugal life and enjoys gardening, Mr Mujica's election is being seen as an expression of the desire for left-wing continuity.
Mr Lacalle was a conservative former president whose administration was mired in corruption.
During military rule prior to 1985, Mr Mujica spent many years in prison.
He was often held in harsh conditions, even spending two years confined to the bottom of a well.
But Mr Mujica acknowledges that those years of imprisonment cured him of pursuing armed struggle.
He has instead sought to build political consensus, successfully bringing the Tupamaro movement into the governing Broad Front coalition.