S
- (Province of Ilocos Sur) Singa
- (Province of La Union) Sinapangan Sur
- (Province of La Union) Sinapangan Norte
- (Province of La Union) Sinapangan
- (Province of La Union) Sinapangan
- (Province of Pangasinan) Sinabodo
- (Province of Ilocos Sur) Sinabaan
- (Province of Ilocos Sur) Sinabaan
- (Province of Pangasinan) Simminoblan
- (Province of Ilocos Sur) Simmanglay
- (Province of Pangasinan) Siminoblan
- (Province of Ilocos Norte) Similla
- (Province of Ilocos Sur) Simaay
- (Province of La Union) Sili
- (Province of Ilocos Norte) Silbung
- (Province of Pangasinan) Silaqui Island
- (Province of Ilocos Sur) Silag
- (Province of Pangasinan) Silag
- (Province of Ilocos Norte) Sidiran
- (Province of Ilocos Norte) Sideg
- (Province of Ilocos Sur) Sibsibbo
- (Province of La Union) Siboan-otong
- (Province of Pangasinan) Siblot
- (Province of Pangasinan) Siapar Island
- (Province of Pangasinan) Siapar
- (Province of La Union) Sevilla Sur
- (Province of La Union) Sevilla Centro
- (Province of Ilocos Sur) Sevilla
- (Province of Pangasinan) Seselangen
- (Province of La Union) Sengngat