Dennis is a census-designated place (CDP) in Labette County, Kansas, United States. As of the 2020 census, the population was 152.
Dennis had its start in the early 1880s by the building of the Memphis, Kansas and Colorado Railroad through that territory. The first post office in Dennis was established in May 1881.
The nearby Big Hill Archeological District is on the National Register of Historic Places.
The community is served by Labette County USD 506 public school district.