Denison is a city in Grayson County, Texas, United States. The population was 22,773 at the 2000 census, but had increased to an estimated population of 23,957 in July 2006. It is also one of two principal cities of and is included in the Sherman, Texas-Denison, Texas Metropolitan Statistical Area. Denison apartments for rent comparison page shows most up to date rent information on Denison apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.