Valentin Yuryevich Demyanenko (Ukrainian: Валенти́н Ю́рійович Дем'я́ненко, romanized: Valentyn Yuriyovych Demyanenko, Azerbaijani: Valentin Yuryeviç Demyanenko [a]), born 23 October 1983 in Cherkassy, Cherkassy Raion, Cherkassy Oblast, Ukrainian SSR, Soviet Union (now Cherkasy, Cherkasy Raion, Cherkasy Oblast, Ukraine), is a former Ukrainian-born Azerbaijani flatwater canoeist.

Demyanenko was a late developer and only came to prominence in 2004 with a shock victory in the C-1 500m final at the European under-23 championships in Poznań, Poland.

In his first international appearance as a senior he won a silver medal at the 2005 European championships in the C-1 200m sprint, just one tenth of a second behind the three-times champion Maxim Opalev of Russia.

[1] The following month, at the 2005 Flatwater Racing World Championships at Zagreb, Croatia, he was entered in two events.

At the senior World Championships in Szeged, Hungary, however he returned to the 200m distance to defend his title.