city, Chelyabinsk oblast (province), western Russia. Troitsk lies along the Uy River at the inflow of the Uvelka River. Founded in 1743 as a fortress, it was chartered in 1784. An agricultural centre for the adjacent steppes, Troitsk also has transport and industrial functions, and a thermal-power station and a nuclear-power plant are located there. The city has colleges for medicine, agriculture, and teacher training. Pop. (1991 est.) 89,800.