A hospital ship is a ship designated for primary function as a floating medical treatment facility or hospital. The four ships of the soviet Ob Class Hospital ships were designed to provide medical and recreational facilities. They were also employed as personnel transports. They have civilian crews but carry uniformed naval medical personnel. The ships are fully equipped with surgical equipment. These are sufficiently well equipped ships, on which can occur all forms of medical aid. The hospitals, placed on the vessels, are capable of assuming to 100 patients simultaneously. On board each of the ships are more than ten therapeutic and diagnostic departments, three operating hall, and the drugstore. Furthermore, on the vessels is a health center, dispensary in 200 places. The Irtysh is in the Pacific Fleet, Svir in the Northern Fleet, and Yenisey in the Black Sea Fleet. The class leader Ob (commissioned in 1980) was stricken in August 1997.

Hospital Ship Yenisey laid down at the Stocznia Szczecinska im. A. Warskiego Shipyard, Szczecin, Poland (yard No.320/2), commissioned 31 January 1981 and was assigned to the Black Sea Fleet.

Now in service.