Sidor Bely or Sydir Bily (1716 — 20 July 1788) was Kosh ataman of the Black Sea Cossack Host.

He took part in numerous sea and land campaigns on the Danube and in Crimea where he gained a reputation as a fine commander and seaman.

He travelled to St Petersburg with Kalnyshevsky and Antin Holovaty in January 1762 for the coronation of Catherine II.

The fate of the Sich was sealed on April 23, 1775, at a council meeting in the Palace to which Bily and Holovaty were not invited.

Some state that he moved to the Danubian Sich, and he was labelled a traitor, that he sold out to the Empress for a gold medal.

Analysis tends to lead us to the fact that Bily was a skillful politician and understood the politics of the time.

Kherson at that time had started building large sail-boats - corvettes, frigates and line boats for the future Black Sea fleet.

Bily took part in the construction of these boats and also in the selection and training of future sailors from the Ukrainian population.

Potemkin's admirals did not know the conditions in the Dnieper-Black Sea region and as a result Bily took a commanding role.

During Catherine II visit through Ukraine and Crimea in 1787, Sydir Bily accompanied her with a guard of Cossacks.