Denys Viktorovych Syzonenko (Ukrainian: Денис Вікторович Сизоненко; born April 13, 1984) is a Ukrainian former swimmer, who specialized in freestyle events. He is a single-time Olympian (2004), and a two-time relay medalist at the Universiade (2003 and 2005). He also trains for Dynamo Kyiv swimming team, under his longtime coach Viktor Turchin. At the 2005 Summer Universiade in Izmir, Turkey, Syzonenko helped out the Ukrainian team (Anton Buhayov, Oleg Lisogor, and Serhiy Advena) to upset their American rivals and claim the medley relay title in a final time of 3:38.49.