Hong Seong-chan (born 30 June 1997)[1] is a South Korean tennis player.

Hong has a career high ATP singles ranking of world No.

[3] Since 2015, Hong has been a member of the South Korean Davis Cup team.

175 he qualified for the ATP 500 Citi DC Open in Washington and defeated Adam Walton and upset third seed Karen Khachanov, for his first top 30 win.

Following semifinal showing at the 2024 International Challenger Zhangjiagang, he reached the top 150 at world No.