"President Donald J Trump spoke today with President Moon Jae-in of the Republic of Korea to congratulate him and the Korean people on his great election victory and their peaceful, democratic transition of power," the White House said in a readout of the phone call.
Both leaders agreed to strengthen the US-South Korea alliance and the "friendship" between the two countries.
"President Trump said he looks forward to working with President Moon and invited him to visit Washington at an early date. President Moon accepted the invitation," the White House said.
The special election was necessitated by the ousting of conservative Park Geun-hye, whose downfall and jailing on corruption charges marked one of the most turbulent stretches in the nation's recent political history.