Left-wing candidate Michelle Bachelet has been elected Chilean president for a second time, defeating her run-off rival by a wide margin.
With nearly 90% of the vote counted, Ms Bachelet had 62% to 38% for Evelyn Matthei, a former minister from the ruling centre-right coalition.
Ms Bachelet first served as president in 2006-10, after which she was obliged by electoral laws to stand down.
She narrowly missed out on outright victory in the first round last month.
"I am happy with the result and victory and I shall be a president for everyone in Chile," Ms Bachelet, 62, said as she received a congratulatory telephone call from outgoing President Sebastian Pinera, according to Reuters.
At a speech to supporters, she said: "I am proud to be your president-elect today. I am proud of the country we've built but I am even more proud of the country we will build."
Ms Bachelet is now set to become the first leader in Chile to serve two terms since the military rule of Gen Augusto Pinochet in 1973 to 1990.
Upon hearing the news, her supporters have been celebrating on the streets by waving flags and sounding car horns in the capital Santiago.
"It is clear at this point. She won. And we congratulate her. Later on, I will go speak with her personally," Ms Matthei, 60, told reporters.
Official results of Sunday's run-off are expected soon. Turnout appears to have been lower than expected.
'Radical' manifesto
A paediatrician by training, Ms Bachelet won 47% of the vote in the first round on 17 November. Ms Matthei secured 25%.
Ms Bachelet leads an alliance of her Socialist Party, Christian Democrats and Communists and has campaigned on policies designed to reduce the gap between rich and poor.
Chile is one of the richest countries in Latin America, but millions have staged protests over the past few years to push for a wider distribution of wealth and better education.
Ms Bachelet wants to increase taxes to offer free university education and reform political and economic structures dating from the dictatorship of Gen Pinochet.
Her manifesto this time is much more radical than before, the BBC's Gideon Long in Santiago reports.
Ms Bachelet was constitutionally barred from serving a second successive term but was very popular when she left office.
Shared childhood
Ms Matthei entered the race after two candidates of the centre-right alliance resigned earlier this year - one for alleged financial irregularities, the other one after struggling with depression.
Evelyn Matthei, 60, has called for a continuation of the policies of outgoing President Sebastian Pinera, asserting that Chileans are "better off" now than when he came to power four years ago.
As children in the 1950s, the current rivals were neighbours and used to play together on the airbase where their fathers, both air force generals, worked.
Evelyn Matthei's father, Fernando, rose through the ranks to run a military school.
Michelle Bachelet's father, Alberto, had a job in the Socialist administration overthrown by Gen Augusto Pinochet in the 1973 coup.
He died in 1974 of a heart attack while in custody. An investigation concluded that the 51-year-old general had probably died of heart problems aggravated by torture at the military academy.
A judge ruled earlier this year that Gen Matthei had no knowledge of or involvement in the torture.
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