Klim Sergeyevich Kostin (Russian: Клим Сергеевич Костин; born 5 May 1999) is a Russian professional ice hockey winger who currently plays with the San Antonio Rampage in the American Hockey League (AHL) while under contract as a prospect for the St. Louis Blues of the National Hockey League (NHL). Considered a top prospect for the 2017 NHL Entry Draft, Kostin was selected 31st overall by the Blues. Kostin previously played for Dynamo Moscow of the KHL, first playing in their junior system, before financial issues led to all the players being released in 2017. Internationally Kostin has played for the Russian national under-18 team at several tournaments.
Kostin debuted for HC MVD in the Junior Hockey League (MHL) during the 2015–16 season. In 30 games for the team he scored 8 goals and 13 assists.
Kostin was selected first overall in the 2016 CHL Import Draft by the Kootenay Ice of the Western Hockey League (WHL), a major junior league in Canada, but he decided to stay in Russia with Dynamo Moscow for the 2016–17 season. He was reluctant to play on a junior team in North America, instead preferring to play for a senior team, either in the NHL or American Hockey League (AHL), the top minor league affiliate for the NHL.