Ellis county is located in western Oklahoma on the Texas state line with Arnett serving as the county seat.

The only major waterway is the Canadian River which is shared with Roger Mills County forming the southern boundary of the county. There are some minor creeks and small rivers in the northern section which eventually empty into Fort Supply Lake in neighboring Woodward County to the east.

This rural county has at least 10 ghost towns including Allmon, 7 miles southwest of Arnett; Chaney, 13 miles northwest of Gage and Greenwood, 6 miles southwest of Fort Supply.

The county population on July 1, 1999, was 4,194, a decrease of 303 over the 1990 census.

Historic sites in the county include the Ellis County Courthouse in Arnett, Eggleston Springs just outside Arnett and the George Carr Ranch House near Camargo.