Rio Maior (Portuguese pronunciation: [ˈʁiu mɐˈjɔɾ]) is a municipality in the Santarém District in Portugal. The population in 2011 was 21,192, in an area of 272.76 km².
The present Mayor is Isaura Morais, elected by the PSD, first woman to be elected a mayor in the municipality. The municipal holiday is November 6.
Administratively, the municipality is divided into 10 civil parishes (freguesias):
- Azambujeira e Malaqueijo
- Marmeleira e Assentiz
- Outeiro da Cortiçada e Arruda dos Pisões
- Rio Maior
- São João da Ribeira e Ribeira de São João
- São Sebastião