Bourne is a town in Barnstable County, Massachusetts, United States. The population was 19,754 at the 2010 census.

For geographic and demographic information on specific parts of the town of Bourne, please see the articles on Bourne (CDP), Buzzards Bay, Monument Beach, Pocasset, Sagamore, and Sagamore Beach.

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Bourne is located at the western end of Cape Cod, with the Cape Cod Canal cutting across the northern portion of the town. It is bordered by Sandwich to the east, Falmouth to the south, Marionand Wareham to the west, and Plymouth and Cape Cod Bay to the north. The town lies approximately 20 miles (32 km) west of Barnstable, 55 miles (89 km) south-southeast of Boston, and the same distance east of Providence, Rhode Island. The border with Plymouth and Wareham in Plymouth County constitutes the only landed border between Barnstable County and any other county (the borders with Dukes and Nantucket counties lie in Nantucket Sound). Major localities of Bourne include Bournedale and Buzzards Bay on the west side of the Cape Cod Canal, Sagamore, which straddles the canal, and Bourne village, Monument Beach, Pocasset, and Cataumet on the east side of the canal.

According to the United States Census Bureau, the town has a total area of 52.9 square miles (136.9 km2), of which 40.7 square miles (105.3 km2) is land and 12.2 square miles (31.6 km2), or 23.11%, is water.

Bourne's geography was formed around its location on Buzzards Bay and the Cape Cod Canal. There are several necks (the local term for a peninsula) and islands along the shore, which create several small coves and harbors. There are also several small ponds and rivers, all of which (except the Herring River, which feeds directly into the Canal) feed into Buzzards Bay. The largest of these inlets, Buttermilk Bay, lies along the border with Wareham. Because of the large parcel of land occupied by Otis A.N.G.B. in the eastern part of the town, the majority of settlement is either along the shores of the Canal or along Buzzards Bay. There is also a small neighborhood (South Sagamore) located between the Canal and the northern boundaries of the base. Bourne has a town forest and a small portion of the Shawme-Crowell State Forest, which is located along Otis's northern boundary. There are also many beaches along its shores, mostly along Buzzards Bay (although Sagamore Beach lies along Cape Cod Bay).