Col. Yuri Ivanovich Onufrienko (Russian: Юрий Иванович Онуфриенко, Ukrainian: Юрій Іванович Онуфрієнко; born 6 February 1961) is a retired Russian cosmonaut. He is a veteran of two extended spaceflights, aboard the space station Mir in 1996 and aboard the International Space Station in 2001–2002.

Onufrienko was born in Ryasne, Zolochiv Raion of Kharkiv Oblast, Soviet Union (now Ukraine). Onufrienko and his wife, Valentina Mikhailovna Onufrienko, have two sons, Yuri, born in 1982 and Aleksandr, born in 1990 and one daughter, Elena, born in 1988. He has two older brothers and his parents are deceased. Onufrienko enjoys tennis, cooking, fishing, chess, and aviation.

Onufrienko graduated from the V.M. Komarov Eisk Higher Military Aviation School for Pilots in 1982 with a pilot-engineer's diploma. In 1994, Onufrienko earned a degree in cartography from Moscow State University.

Onufrienko was awarded the Hero of Russia medal, the title of Pilot-Cosmonaut of the Russian Federation, the Gold Star Medal of the Hero of the Russian Federation and NASA Space Flight and Public Service Medals. In 1997 he was named a Chevalier in the French Legion of Honor.

Onufrienko served as a pilot in the Soviet (later Russian) Air Force, where he logged over 800 flight hours. He has flown the L-29, Sukhoi Su-7, Sukhoi Su-17 (M1-4), and L-39.

Onufrienko was selected as a cosmonaut candidate in 1989. From September 1989 to January 1991, he underwent a course of general space training. Starting April 1991, he underwent training as a member of test cosmonauts group. Starting March 1994, he entered flight training to be the commander of the stand-by crew of the Mir-18 expedition aboard the Soyuz TM-21 spacecraft and the Mir space station as part of the Shuttle-Mir program.

From February 21 to September 2, 1996, Onufrienko served as commander of the Mir EO-21 expedition. The Soyuz TM-23 spacecraft carrying Onufrienko with cosmonaut Yury Usachov lifted off from the Baikonur Cosmodrome on February 21, 1996, at 12:34:05 UTC. After two days of autonomous flight, the Soyuz spacecraft docked with the Mir space station's forward-facing port on February 23 at 14:20 UTC. One month later, he and Yuri Usachov were joined by NASA astronaut Shannon Lucid. During Mir-21 Onufrienko performed numerous research experiments including Protein crystal growth experiments experiments in materials science using high temperature melting oven "Optizon". The new module Priroda, the seventh and final module of the Mir Space Station arrived on April 26, 1996. Its primary purpose was to conduct Earth resource experiments through remote sensing and to develop and verify remote sensing methods. During Mir EO-21 supplies arrived with the Progress M-31 spacecraft. Onufrienko and Yuri Usachov were joined by French astronaut Claudie André-Deshays after the departure of Shannon Lucid.

On September 2, 1996, Onufrienko, Usachev and Claudie André-Deshays returned to Earth on board the Soyuz TM-23 capsule. The spacecraft landed at 07:41:40 UTC 108 km south west of Akmola (Tselinograd). Altogether, on board Soyuz TM-23 and Mir, Onufrienko logged 193 days in space.