Voting has begun in Columbia’s first presidential election since the government signed a peace agreement with the Farc rebel group in 2016.
Incumbent Juan Manuel Santos cannot stand again, after serving two terms.
The main contenders are conservative Ivan Duque, who has opposed the peace deal, and left-winger Gustavo Petro, an ex-guerrilla and former Bogota mayor.
Polls suggest that neither will win 50% of the vote on Sunday and they will face each other in a run-off in June.
President Santos, a centre-right politician, sought to end the decades-long conflict with the Revolutionary Armed Forces of Colombia (Farc), the country’s main guerrilla group.
The peace deal he signed in 2016 was reached after years of negotiations. But it was regarded as too lenient by many voters and rejected in a referendum.
A revised accord was approved by Congress later that year.
Mr Duque, who is leading in opinion polls, campaigned against the agreement and has promised to reverse some of its provisions if he becomes president.
Mr Petro is a former member of the M-19 rebel group who backs the deal. If elected he would be Colombia’s first-ever left-wing president.
Correspondents say that with the main civil conflict over, voters are much more worried about economic issues.
The candidates have mainly campaigned on issues such as inequality, unemployment, housing and corruption.
Also standing in the election are:
- Sergio Fajardo, a left-leaning former mayor of the city of Medellin
- German Vargas Lleras, a former housing minister
- Humberto de la Calle, a government peace negotiator
About 100 international observers are monitoring the elections.