The Constitutional Court ruled Friday to formally end Park's presidency over a huge political scandal involving her and her longtime confidante. By law, South Korea must hold a national vote to find her successor within two months of the ruling.
The Ministry of Interior said Wednesday that May 9 has been chosen as the date for the election.
Moon Jae-in, a liberal opposition leader who lost the 2012 presidential election to Park, is the favorite to be the country's next leader in opinion surveys.
Prosecutors accuse Park of colluding with confidante Choi Soon-sil to extort money from businesses and allowed her pull government strings from the shadows.