Sergey Yurievich Polonsky (born 1 December 1972) is a Russian businessman. Polonsky is the owner and head of one of the largest real estate companies, Mirax Group (2004–2011). He was one of the richest men in Russia before the late-2000s financial crisis. Now he is shareholder and investor of a number of commercial structures incorporated by the holding Potok (as of 1 December 2011), earlier Nazvanie.net (March – November 2011). In October 2011, Sergey Polonsky was noted by the Forbes magazine as one of the nine most unusual Russian businessmen. He is currently awaiting trial in Moscow on charges of fraud.

The embezzlement charges, Polonsky believes, are part of an attempt by FTsSR and the Moscow government to take the Kutuzovskaya project away from him and hand control to Arkady Rotenberg a rival property developer with close ties to the Russian president Vladimir Putin.