Cherbourg-Octeville is a city and former commune situated at the northern end of the Cotentin peninsula in the northwestern French department of Manche. It is a subprefecture of its department, and was officially formed when the commune of Cherbourg absorbed Octeville on 28 February 2000. On 1 January 2016, it was merged into the new commune of Cherbourg-en-Cotentin. The city is a Maritime prefecture and sub-prefecture of la Manche. Due to its union, it is the most populated city in its department with 37,121 inhabitants making it the first city of the department before the Saint-Lô prefecture and the second in the region after Caen.
Cherbourg-en-Cotentin is protected by Cherbourg Harbour, between La Hague and Val de Saire, and the city has been a strategic position over the centuries, disputed between the English and French. Cited as one of the "keys to the kingdom" by Vauban, it became, by colossal maritime development work, a first-rate military port under the leadership of Louis XVI and Napoleon, and holds an arsenal of the French Navy.