The 1966 Torneo Descentralizado was the 50th season of the highest division of Peruvian football. This season marked the first time the Primera División was named the Descentralizado because teams outside Lima and Callao were invited for the first time making it the first national championship in Peru.
The first match of the season was played on 13 August 1966 between Universitario and Mariscal Sucre in the Estadio Nacional. Shortly after this match, the first match to feature a team outside the Lima and Callao region was between Sporting Cristal and Alfonso Ugarte de ChiclÃÂn in the same stadium on the same day.
The champion was Universitario. Four teams were relegated at the end of the season. Carlos Concha was relegated to the 1967 Segunda División as the last placed team. In addition, Octavio Espinosa, Alfonso Ugarte, and Melgar were relegated as they needed to place seventh or higher to remain in the first division. They needed to play the 1967 Copa Perú to attain promotion to the first division.
It was established that fourteen teams would participate in this first national tournament. Given that the necessary financial support to fund a complete transformation was lacking, the process was carried out gradually. Thus, the first Descentralizado tournament retained a still centralist structure: ten teams from Lima and four from the provinces.
The four teams invited to play in the inaugural national championship were the district champions of Arequipa, Ica, Piura, and Trujillo: Melgar, Octavio Espinosa, Atlético Grau, and Alfonso Ugarte de ChiclÃÂn, respectively.