Konstanty Iwanowicz Ostrogski (c. 1460[1] – 10 August 1530;[2] Lithuanian: Konstantinas Ostrogiškis) was a Ruthenian prince and magnate of the Grand Duchy of Lithuania.

For his victory near Ochakiv against Mehmed I Giray's forces he was awarded with the title of Grand Hetman of Lithuania.

In 1514, another war with the Grand Duchy of Moscow started and he became the commander in chief of all the Polish and Lithuanian forces (amounting to up to 35,000 soldiers).

Among his subordinates were Jerzy Radziwiłł, Janusz Świerczowski [pl], Witold Sampoliński and the future Hetman of the Crown Jan Tarnowski.

On 8 September 1514 he achieved a significant victory in the Battle of Orsha, defeating the army of Vasili III of Russia.