Puerto de Mejillones is a province in the western parts of the Bolivian department of Oruro. It is one of the sixteen provinces in the Oruro Department. Its seat is La Rivera.

Oruro is a department of Bolivia, with an area of 53,588 km2 (20,690 sq mi). Its capital is the city of Oruro. According to the 2012 census, the Oruro department had a population of 494,178.