a river in Kursk and Lipetsk oblasts, RSFSR, partially along the border of Orel Oblast; a right tributary of the Sosna River (Don basin). The Olym is 151 km long and drains an area of 3,090 sq km. It originates in the Central Russian Upland and flows along the upland to the north. The river is fed primarily by snow. High water occurs in April. The mean flow rate 63 km from the mouth of the Olym is 6.5 cu m per sec; the maximum is 674 cu m per sec and the minimum, 0.63 cu m per sec. The river freezes in November and thaws in March and April.