Mosteiro is the smallest civil parish in the municipality of Lajes das Flores on the Portuguese island of Flores, in the archipelago of the Azores. The population in 2021 was 19, in an area of 5.99 square kilometres (2.31 sq mi).

Lajes das Flores is a municipality in the western part of the Azores; it includes the southern part of the island of Flores. To the north, where it is bordered by Santa Cruz das Flores. The population in 2021 was 1,408, in an area of 70.05 square kilometres (27.05 sq mi). Its municipal seat is in the parish of the same name.