Yoon Dong-Sik (born August 24, 1972 in Seoul) is a Korean judoka, and mixed martial artist currently competing in DREAM.

Yoon made his MMA debut at PRIDE Total Elimination 2005 against legendary Japanese fighter Kazushi Sakuraba. It was a heavily anticipated matchup in both Japan and Korea due to the rivalry between the two nations and it was Sakuraba's comeback match after a ten month absence due to injuries. With a lack of MMA experience and knowledge, Yoon lost to Sakuraba only 38 seconds into the match. After the match, Yoon accepted the offer to join Sakuraba's Takada Dojo. Yoon tasted his first victory in MMA at the K-1 Dynamite!! USA event, where he scored a surprising submission win over heavily favored Dutch kickboxer Melvin Manhoef. Yoon went on to win his second consecutive fight at HERO'S by beating former Cage Rage champion Zelg Galesic by armbar after only 1 minute 29 seconds.

On October 28, 2007 Yoon also beat Fabio Silva by armbar submission making that his third win in K-1 Hero's, his third victory in MMA, and his third consecutive win by armbar. His newfound propensity for finishing opponents with an armbar has led to fans and journalists dubbing the move the "Dongbar" when performed by Yoon.