Kasimov is a town located in the Ryazan Oblast of Russia. It is situated on the left bank of the Oka River.
According to census data, the population of the town has fluctuated over time. The 2010 census recorded a population of 33,491, while previous records show 35,816 in 2002, 37,521 in the 1989 Soviet census, and 17,000 in 1910.