Park Geun-Hye, the daughter of a former South Korean dictator, on Tuesday formally announced her bid to become the country's first woman president and vowed to work for a fairer economy.
Park is widely expected to secure the ruling conservative New Frontier Party's nomination at its primary next month. She is also considered the front-runner in the 19 December election.
"I will devote my everything to make the Republic of Korea (South Korea) a country in which everybody can achieve their dreams," she said in a speech.
Park, now 60, narrowly lost the conservative party's nomination to Lee Myung-Bak in 2007. He went on to become president but is constitutionally barred from standing again.
Park pledged to work for a fair and transparent market economy and to push for "economic democratisation" amid a widening wealth gap in Asia's fourth largest economy.
She also promised to expand welfare programmes and ease tense relations with North Korea.
Park's father Park Chung-Hee seized power in a coup in 1961 and ruled until his assassination in 1979 by his spy chief. Her mother was shot dead by a pro-North Korean assassin in 1974.