Semyon Semyonovich is a member of the Duty faction who appears in S.T.A.L.K.E.R.: Clear Sky. He is one of five unique NPCs spawned into Kolobok's bar at the Duty base, the other four being Milutin, Mister, Fyokl, and Bandicoot.
Although Semyon Semyonovich spawns in Kolobok's bar, he is seldom to be found there. Instead, he is typically found patrolling the Duty base or keeping watch on one of the guard towers.
- Semyon Semyonovich is set to sell the coordinates of two stashes in Yantar – 'Booth with switchboard' and 'Cistern bellmouth' – but due to a missing dialog option, these can never be acquired by the player in the unmodified game.
- Of the five bar stalkers, Semyon Semyonovich is the only one whose name is not mononymous.
- Character name is a reference to the Soviet film "The Diamond Arm" with Yuri Nikulin as Semyon Semenych.