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 Lacalle has conceded victory.
Mr Mujica succeeds a popular head of state, Tabare Vasquez, 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 Tupamaru movement into the governing Broad Front coalition.
Mujica’s victory also gave the Broad Front a narrow majority in Congress, where his wife, Sen. Lucia Topolansky, was the top-vote getter and therefore is now third in line to the presidency, after vice president-elect Danilo Astori.
Lacalle, a scion of Uruguay’s political elite, finished second with 29 percent in October’s first-round election, and picked up most of the third-place, right-wing Colorado Party voters, but it wasn’t enough to defeat Mujica.
Mujica, 74, vowed to do everything possible to build bridges and avoid creating an atmosphere of tension and drama. He said negotiation and dialogue would be his tools, and cited Brazilian President Luiz Inacio Lula da Silva as his inspiration.
The National Party traded power with the right-wing Colorado Party for 150 years until the Broad Front pulled enough leftist factions together five years ago to give Vazquez a presidential victory.
Many voters said the single five-year term required by Uruguay’s constitution wasn’t enough to consolidate the successes of Vazquez, a Marxist oncologist and former Montevideo mayor who enjoyed 71 percent approval ratings in a poll this month. Vazquez imposed a progressive income tax, using the additional revenue to lower unemployment and poverty, provide equal access to health care to everyone under 18 and steer the economy to 1.9 percent growth this year even as many other economies shrank.
Lacalle, in contrast, was a champion of privatization during his 1990-95 term and vowed this time to eliminate the income tax and “take a chain saw” to state bureaucracies. But he also acknowledged Vazquez’s successes, saying he would make no major changes in economic policies.
Mujica co-founded the Tupamaros, one of many Latin American leftist rebel groups inspired by the Cuban revolution in the 1960s to organize kidnappings, bombings, robberies and other attacks on U.S.-backed right-wing governments. Convicted of killing a policeman in 1971, he endured torture and solitary confinement during nearly 15 years in prison.
Topolansky also was a Tupamaro leader, and like Mujica, was tortured during more than 13 years in prison.
In the quarter-century since the dictatorship ended and they were granted amnesty, the couple transformed the guerrillas into a legitimate political movement that is now the driving force behind the Broad Front.
In a July speech, Mujica vowed to distance the left from “the stupid ideologies that come from the 1970s — I refer to things like unconditional love of everything that is state-run, scorn for businessmen and intrinsic hate of the United States.
“I’ll shout it if they want: Down with isms! Up with a left that is capable of thinking outside the box! In other words, I am more than completely cured of simplifications, of dividing the world into good and evil, of thinking in black and white. I have repented!”
But Mujica still has the appearance of an anti-politician, a gruff old man more comfortable driving a tractor on his farm than shuffling through marbled halls.
“This isn’t too exciting — at this point it’s like dancing with your sister,” he said enigmatically as he cast his ballot.
Lacalle called for national unity after casting his vote, urging Uruguayans to treat each other with respect once the results are known.