Yesaul (Turkic: yasaul="chief"; Russian: есау́л), a post and a rank in the Cossack units.

Originally it was introduced by Stefan Batory, king of Poland in 1576.

Cossacks in Russia

There were different Yesaul posts and ranks in Muscovy and Imperial Russia:

• Генеральный есаул (Generalny yesaul) - General Yesaul
• Походный есаул (Pokhodny yesaul) - Campaign Yesaul
• Полковой есаул (Polkovoy yesaul) - Regiment Yesaul
• Артиллерийский есаул (Artilleriysky yesaul) - Artillery Yesaul
• Сотенный есаул (Sotenny yesaul) - Yesaul of a sotnya
• Станичный есаул (Stanichny yesaul) - Yesaul of a stanitsa
• Войсковой есаул (Voiskovoy yesaul) - Yesaul of the cossack voisko

In 1798-1800, the rank of Yesaul was equated with the ranks of Rittmeister in cavalry and Captain in infantry.