St. Peter-Pagig is a former municipality in the district of Plessur in the Grisons, Switzerland. It was formed on 1 January 2008 through the merger of St. Peter and Pagig. On 1 January 2013 the former municipalities of St. Peter-Pagig, Calfreisen, Castiel, Langwies, Lüen, Molinis and Peist merged into the municipality of Arosa.
Before the merger, St. Peter-Pagig had a total area of .
The former municipality is located in the Schanfigg sub-district of the Plessur district on the northern side of the mid-Schanfigg valley.
On the border with the municipality of Molinis is the Sankt Peter-Molinis railway station, on the Chur-Arosa railway line.
St. Peter-Pagig had a population (as of 2010) of 214.
St. Peter had a population () of 241. The historical population is given in the following table: