Kovalchuk became the first player born in Russia to be taken with the No. 1 pick in the NHL Draft when the Atlanta Thrashers selected him in 2001. The native of Tver, Russia, stepped into the NHL as an 18-year-old in 2001-02 and had 51 points (29 goals, 22 assists) in 65 games, missing the final 17 with a shoulder injury.

He finished second to teammate Dany Heatley in voting for the Calder Trophy as the top rookie in the NHL. Kovalchuk scored 38 goals in his second NHL season, then had 41 in 2003-04 to tie for the Maurice Richard Trophy as the League's top goal-scorer. He scored 52 in 2005-06 and again in 2007-08, had 43 in 2008-09 and scored 31 times in 49 games in 2009-10 before being traded to the New Jersey Devils on Feb. 4, 2010, then signed a 15-year contract with the Devils on Sept. 3, 2010.

Kovalchuk set NHL records in 2011-12 with 11 shootout goals and seven game-deciding goals, and he helped the Devils advance to the 2012 Stanley Cup Final.

He announced his retirement from the NHL on July 11, 2013, and played the next five seasons with SKA Saint Petersburg of the Kontinental Hockey League, where he was named MVP of the Gagarin Cup playoffs in 2015. Kovalchuk returned to the NHL with the Los Angeles Kings on July 1, 2018, signing a three-year contract.

His contract was terminated by the Kings on Dec. 17, 2019, and he joined the Montreal Canadiens on Jan. 3, 2020, scoring his first goal eight days later. The Canadiens traded him to the Washington Capitals on Feb. 23, 2020, enabling him to realize a dream of playing with longtime friend and fellow Russian Alex Ovechkin - the two first met each other as teens at a hockey camp in Russia.