Park Geun-hye becomes country's first female leader after rival candidate Moon Jae-in concedes defeat.
The daughter of South Korea's former military ruler has won the country's presidential election, promising in a speech to her supporters to heal a "divided society".
The win over her liberal rival Moon Jae-in on Wednesday makes Park Geun-hye the country's first female head of state.
The office of South Korean President Lee Myung-bak congratulated party colleague Park on her win, even before officials had finished counting votes.
The 60-year old conservative Park will now return to the presidential palace where she served as her father's first lady in the 1970s, after her mother was assassinated by a North Korea-backed gunman.
With 92 per cent of the national vote counted, Park had an insurmountable lead of 51.6 per cent to the 47.9 per cent of Moon, her liberal rival, according to the country's election commission.
Her raucous, jubilant supporters braved sub-zero temperatures to chant her name and wave South Korean flags outside her house. When she reached her party headquarters, Park was greeted with shouts of "president".
An elated Park reached into the crowd to grasp hands of supporters wearing red scarves, her party's colour.
"This is a victory brought by the people's hope for overcoming crisis and economic recovery," she said. "I will be a president who fulfills in every way the promises I made to the people."
High voter turnout
The election was marked by a high turnout of more than 75 per cent, compared to 63 per cent in the 2007 presidential poll.
Park is the daughter of one of modern Korea's most polarising figures, the late leader Park Chung-hee, who is both admired for dragging the country out of poverty and reviled for his ruthless suppression of dissent during 18 years of autocratic rule.
Moon, who was chief of staff to the late left-wing president Roh Moo-hyun, is a former human rights lawyer who was once jailed for protesting against the Park Chung-hee regime.
"I feel so sorry and guilty that I have failed to accomplish my historic mission to open a new era of politics," Moon told reporters outside his Seoul residence. "I humbly accept the outcome of the election," he added
Al Jazeera's Harry Fawcett, reporting from Seoul, said that Park had been able to appeal to enough of "middle ground" voters to swing the poll in her favour.
"This conservative candidate, who has really tacked away from some of the more right wing policies of her party, seems to have done enough not just to consolidate her own core constituency vote, but also to appeal to enough of a middle ground in this very high turnout election," he reported.
"This is still a divided country in terms of generations, party lines and regions. People have stuck to quite long-held party allegiances."
Engagement with N Korea
Both candidates' campaigns highlighted the need for "economic democratisation" - a campaign term about reducing the social disparities caused by rapid economic growth - and promised to create new jobs and increase welfare spending.
Matthias Maass, assistant professor of international relations at Yonsei University in Seoul, told Al Jazeera that domestic politics had driven campaigns for both sides.
"The issues include the country's economy, talk about measures to address a low birth rate, questions of unemployment, the wealth income gap, and social injustice," Maass said.
The new president will face numerous challenges, including a belligerent North Korea, a slowing economy and soaring welfare costs in one of the world's most rapidly ageing societies.
While both candidates had signalled a greater engagement with North Korea, Park's approach was more cautious than Moon's promise to resume aid without preconditions and seek an early summit with North Korean leader Kim Jong-un.
Park has promised strong leadership that would steer the country through the challenges of global economic troubles.
"I have no family to take care of and no children to pass wealth to. You, the people, are my family and your happiness is the reason that I stay in politics," Park, who has never been married, said in a televised press conference on Tuesday.