Reynogüelén, also spelled Reinogüelén, Reinohuelén, and Reynohuelén, was the original Mapudungun name of the eastern regions of what are now the communes of Parral in Linares Province, and Ñiquén, and San Carlos communes in the Ñuble Province of the Biobio Region of Chile.
San Carlos is bordered on the west by the commune of Ninhue, on the north by Ñiquén and Cauquenes (the latter in Cauquenes Province), on the east by San Fabián, and on the south by San Nicolás, Chillán and Coihueco.