The Raptors flew over the US military air base in Osan in Gyeonggi province, bordering North Korea, on Wednesday.
The move comes as the US and South Korea discuss possibly deploying a missile defence system in the South.
North Korea's actions have attracted international condemnation and calls for new UN sanctions.
Relations with the South have deteriorated, with Seoul suspending operations of the jointly-run Kaesong industrial park.
The US Raptors, one of the world's most advanced military aircraft, were flown into South Korea from their base in Okinawa in Japan.
South Korea' Yonhap news agency said the deployment of four stealth jets by the US at one time was rare. Read more on bbc.