San Fabián is the westernmost of 21 communes in the Ñuble Province of central Chile's Biobío Region. The capital is the town of San Fabián de Alico. The commune spans an area of 1,568.3 km2 (606 sq mi).
As a commune, San Fabián is administered by a municipal council, headed by a directly elected alcalde. For the years 2008-2012, the alcalde is Cristían Marcelo Fernández Gómez (Ind.), and the council members are:
Within the electoral divisions of Chile, San Fabián is represented in the Chamber of Deputies as a part of the 42nd electoral district (together with Ñiquén, San Carlos, San Nicolás, Ninhue, Quirihue, Cobquecura, Treguaco, Portezuelo, Coelemu, Ránquil, Quillón, Bulnes, Cabrero, Yumbel). The commune is represented in the Senate as part of the 12th senatorial constituency (Biobío Cordillera).