Participants wave a rainbow flag as they march on a street during the Korea Queer Culture Festival 2022 in central Seoul, South Korea, July 16, 2022.
Under the country's military criminal act, members of the armed forces face up to two years in prison for same-sex relationships.
The law has been referred to the court and upheld by it four times since 2002.
In Thursday's five-to-four ruling, the court said allowing same-sex relations could undermine discipline within the military and harm its combat capabilities.
South Korea has one of the world's largest active armies, with all able-bodied men between the ages of 18 and 28 required to serve between 18 and 21 months.
Persons:
Heo, Activists, Boram Jang, Soo, hyang Choi, John Stonestreet
Organizations:
Korea Queer Culture, REUTERS, Rights, Amnesty, Thomson
Locations:
Korea, Seoul, South Korea, Rights SEOUL, East Asia