Kostiantyn Ivanovycz Ostrogski (c. 1460 – August 10, 1530) is a magnate of the Grand Duchy of Lithuania and later a Grand Hetman of Lithuania from September 11, 1497 until his death.

As a speaker of the Ruthenian language he is considered to be one of the precursors of the Belarusian language and a national hero in Belarus.