Update: Former student activist Gabriel Boric won the Chilean election with 56 percent of the vote in the runoff. Read the latest.
The two men have strikingly different views of the kind of country Chile should be. José Antonio Kast, a former lawmaker from the right-wing Christian Social Front, opposes abortion, is critical of migration and promises law and order.
Gabriel Boric, a lawmaker with the left-wing I Approve Dignity coalition, wants to reform systems that many in Chile believe are the source of inequality in the prosperous South American nation: education, health care and government pensions.
Some see Chile as another country drawn to extremes, with no space for a middle ground. Kast won 28 percent of the vote to lead the first round of the election last month; Boric was second with 26 percent.
This is one of the most tightly disputed elections since Chile became a democracy after the end of the Pinochet dictatorship in 1990.