Illya Vasylovych Marchenko (Ukrainian: Ілля Васильович Марченко) (born 8 September 1987) is a Ukrainian professional tennis player. Marchenko turned professional in 2005 and had been playing at the Futures and Challengers level from 2005–2008. His career high in singles is No. 49 (26 September 2016) and 268 in doubles (August 25, 2014). On the ATP Tour, Marchenko reached the semifinals of Moscow in 2009 and Doha in 2016.
He is noted for his backhand, which he cites as his best shot. His favorite surface is hard courts.
Illya began playing tennis at age seven. His father Vassili and mother Anna are both engineers. Has one older brother, Igor Marchenko, a manager and former ice skater who took part in the 1998 Winter Olympics. Growing up, he admired Lleyton Hewitt and Roger Federer. He has played doubles on the Futures level with fellow Ukrainian Artem Smirnov. He has been coached by Orest Tereschuk since July 2009.