Decimomannu (Sardinian: Deximumannu or Déximu Mannu [ˌdeʒimuˈmanːu]) is a comune in the Metropolitan City of Cagliari, Sardinia, Italy.

[2] Decimomannu borders the municipalities of Assemini, Decimoputzu, San Sperate, Siliqua, Uta, Villasor, and Villaspeciosa.

[3]Decimomannu's origins date back at least to Roman times, as attested by its Latin name, meaning "the biggest town located ten miles from Cagliari".

The Battle of Lucocisterna, fought between the Pisane and the Aragonese, took place here in 1324, and after it the town belonged to the latter (with the exception of a short period under the Giudicato of Arborea in 1353-1355).

It is a long-term collaboration between the Italian Air Force and Finmeccanica to train military pilots on modern flight simulators.