Ruslan Ponomariov (Ukrainian: Руслан Пономарьов; Russian: Русла́н Пономарёв) (born October 11, 1983) is a Ukrainian chess player and former FIDE world champion.
Ponomariov was born in Horlivka in Ukraine to parents of Russian ethnicity. In 1994 he placed third in the World Under-12 Championship at the age of ten. In 1996 he won the European Under-18 Championship at the age of just twelve, and the following year won the World Under-18 Championship. In 1998, at the age of fourteen, he was awarded the Grandmaster title, making him the youngest ever player at that time to hold the title. In 1999, he was a member of the Ukrainian national youth team, which won the U-16 Chess Olympiad in Artek, Ukraine.
Among Ponomariov's notable later results are first at the Donetsk Zonal in 1998, 5/7 in the European Club Cup 2000 (including a victory over then-FIDE World Champion Alexander Khalifman), joint first with 7½/9 at Torshavn 2000, 8½/11 for Ukraine in the 2001 Chess Olympiad in Istanbul, winning gold medal on board 2, and first place with 7/10 in the 2001 Governor's Cup in Kramatorsk.
In 2002 he beat his fellow countryman Vassily Ivanchuk in the final of the FIDE World Chess Championship 2002 by a score of 4½-2½ to become FIDE world champion at the age of 18, the first teenager and youngest person to ever become FIDE world champion. However, he is not the youngest undisputed world champion due to the split of the World Chess Championship.
In the same year he finished second in the very strong Linares tournament, behind Garry Kasparov. His result in the strong 2003 Corus tournament at Wijk aan Zee was not as good - despite having the third highest Elo rating, he finished only joint eleventh out of fourteen players with 6/13, and at Linares the same year he finished only fifth out of seven with 5½/12.
There were plans for him to play a fourteen-game match against Kasparov in Yalta in September 2003, the winner of which would go on to play the winner of a match between Vladimir Kramnik and Péter Lékó as part of the so-called "Prague Agreement" to reunify the World Chess Championship (from 1993 until 2006 there were two world chess championships). However, this was called off after Ponomariov refused to sign his contract without reservation.
Ponomariov remained FIDE champion until Rustam Kasimdzhanov won the FIDE World Chess Championship 2004.
He finished in the top 10 in the 2005 FIDE World Cup, which qualified him for the Candidates for the FIDE World Chess Championship 2007, being played in May-June 2007. He was eliminated in the first round, losing 3½-2½ to Sergei Rublevsky.
In his games with white, Ponomariov has almost always played 1. e4, entering the main lines of the Ruy Lopez and Sicilian Defence. With black, he has played the Sicilian against 1. e4 and also replied 1... e5, going into the Ruy Lopez. Against 1. d4 he has adopted a variety of defences, including the Queen's Gambit Accepted, the Queen's Indian Defence and the King's Indian Defence. Earlier in his career he experimented with the Benko Gambit and Pirc Defence, but as of 2003 these have fallen out of his repertoire.