Dennis is a town in Barnstable County, Massachusetts, United States, located near the center of Cape Cod. The population was 14,674 at the 2020 census.

The town encompasses five distinct villages, each of which has its own post office. These constituent villages are Dennis (including North Dennis), Dennis Port, East Dennis, South Dennis, and West Dennis.

Dennis was first settled by Europeans in 1639, by John Crowe (later Crowell), Antony Thacher, and Thomas Howes, as part of the town of Yarmouth. It was known then as the East Precinct. The original inhabitants who preceded English settlers called the northern sections of town Nobscuesset, Sesuit, and Quivet.

The town officially separated and incorporated in 1793. It was named after resident minister, Rev. Josiah Dennis. There was not enough land for farming, so seafaring became the town’s major industry in its early history, centered around the Shiverick Shipyard.

Currently, Dennis is a popular seaside resort town, notable for its stately colonial mansions along the northern Cape Cod Bay coastline, and its picturesque, warm-water beaches along the southern Nantucket Sound.

The Cape Playhouse, in northern Dennis, is one of the oldest summer theatres in the United States and among the best known. Actress Bette Davis was “discovered” while working there as an usher. Other notable past and present Dennis residents include author Mary Higgins Clark (1927–2020) and actress Amy Jo Johnson, who grew up in Dennis.