 Cherbourg-en-Cotentin is located at the northern tip of the Cotentin Peninsula, in the department of Manche, of which it is a subprefecture.At the time of the 1999 census the city of Cherbourg had an area of , while the city of Octeville had an area of .The largest city in the Department of Manche, it is the result of the merger of the communes of Cherbourg and Octeville.