Yun Sung-hwan (Korean: 윤성환; born October 8, 1981, in Busan, South Korea) is a starting pitcher for the Samsung Lions of the KBO League.
He led his team to two consecutive gold medals in the baseball tournament at the Korean National Sports Festival in 2000 and 2001, and helped his team to win their first national baseball championship as a starter and closer in 2002.
Yun was selected by the Samsung Lions in the 2nd round (8th pick, 15th overall) of the 2004 KBO Draft.
Yun wanted to join the Lotte Giants, the team from his hometown, however, head coach Sun Dong-yol, currently the manager of Samsung Lions saw great potential in Yun and scouted him.
On July 30, 2009, Yun pitched the whole game for the first time in his pro career against the LG Twins.