Treguaco (Spanish pronunciation: [tɾeˈɣwako]), also spelled as Trehuaco ([tɾeˈwako]), is a Chilean city and commune in Itata Province, Ñuble Region.

The commune's population fell by 6% (341 persons) between the censuses of 1992 and 2002 (0.6% annual loss).

As a commune, Treguaco is a third-level administrative division of Chile administered by a municipal council, headed by an alcalde who is directly elected every four years.

), and the council members are:[1][2] Within the electoral divisions of Chile, Treguaco is represented in the Chamber of Deputies as a part of the 42nd electoral district (together with San Fabián, Ñiquén, San Carlos, San Nicolás, Ninhue, Quirihue, Cobquecura, Portezuelo, Coelemu, Ránquil, Quillón, Bulnes, Cabrero and Yumbel).

The commune is represented in the Senate as part of the 13th senatorial constituency (Biobío Cordillera).