Laura Chinchilla had 47% of the vote with nearly all the votes counted.

The closest contender, Otton Solis of the Citizens Action Party, had 25%. He and the other main rival quickly conceded defeat.

Chinchilla, a protege of the current president, Nobel Peace Prize winner Oscar Arias, campaigned on a promise to continue the government's free market economic policies.

Chinchilla, who served as vice president under Arias, was well over the 40% needed to avoid an April run-off.

Solis barely lost the presidential election to Arias in 2006, but many opposition voters went over to tax-bashing Libertarian candidate Otto Guevara, who had 21% of the votes.

Solis congratulated Chinchilla on her apparent victory. "She is going to be the next president of Costa Rica," he told supporters. Guevara offered congratulations to "our president, Laura Chinchilla".

Arias' economic policies brought Costa Rica into the Central American Free Trade Agreement with the United States and initiated trade relations with China after a 63-year association with Taiwan. But critics of the government argued that Arias' administration catered to big developers to boost the economy at the cost of the nation's fragile ecosystems.

Both Solis and Guevara portrayed Arias' centrist National Liberation Party as stagnant and ridden with old-school Latin American cronyism. But most Costa Ricans were reluctant to shake up the status quo in a country with relatively high salaries, the longest life expectancy in Latin America, a thriving ecotourism industry and near-universal literacy.

Chinchilla, a 50-year-old mother and a social conservative who opposes abortion and gay marriage, appealed both to Costa Ricans seeking a fresh face in politics and those reluctant to risk the unknown.