Sergei Ratnikov (born 21 November 1959) is an Estonian professional football manager and former player. He last managed Levadia in Estonian Meistriliiga.
Two of Ratnikov's sons, Eduard Ratnikov and Daniil Ratnikov, are footballers.
Ratnikov played for the Estonia national football team during the 1990s. He earned his first official cap on June 3, 1992, when Estonia met Slovenia in a friendly.
He has played for clubs like FC Flora Tallinn, FC Nikol Tallinn, and in Finland for VIFK Vaasa and FF Jaro.
Meistriliiga Manager of the Month: July 2013, March 2014