Slavi Kostenski (; born 21 March 1981) is a former Bulgarian footballer who played as a defender. He is the head coach at Chernomorets Burgas.
Kostenski was raised in Chernomorets Burgas's youth teams. Then he played for Slavia Sofia and kazakhstani football club FC Irtysh.
In 2012 Kostenski moved to Gozo, Malta and signed with Xagçra United, where he played 13 matches and scored 2 goals.