Ruslan Shamilevich Chagaev (Tatar: Руслан Шамил улы Чагаев, Ruslan Şamil ulı Çağayev; Uzbek: Ruslan Shamil'evich Chagaev; Russian: Руслан Шамилович Чагаев); born 19 October 1978) is a retired Uzbek professional boxer of Tatarian descent who competed from 2001 to 2016. He held the WBA heavyweight title twice, from 2007 to 2009 and from 2014 to 2016, and was the first Asian boxer to win a world heavyweight title by any of the four major sanctioning bodies.
Chagaev's career is outstanding in a sense he is one of a few professional boxers to resume his amateur career after a few professional bouts in 1997. Chagaev was reinstated as an amateur by AIBA the following year as his professional bouts were declared exhibitions.
In 2007, Chagaev defeated then-unbeaten Nikolai Valuev to win his first WBA heavyweight title, and would make two successful defences. Due to injuries and being unable to grant Valuev a rematch in 2009, the WBA stripped Chagaev of the title. He went on to suffer his first professional loss in the same year to unified heavyweight champion Wladimir Klitschko.