The Castle of Monsanto is a medieval castle located in the civil parish of Monsanto e Idanha-a-Velha, in the municipality of Idanha-a-Nova, Portuguese district of Castelo Branco.

The Castle of Monsanto is a breathtakingly beautiful 12th-century castle located in the hills of Monsanto e Idanha-a-Velha, in the municipality of Idanha-a-Nova. It was built by D. Afonso I of Portugal as part of a defensive line for the region. The castle has four towers and a keep, a chapel, a church, and many defensive walls and ramparts. Throughout its long history it has weathered several sieges and restorations. Visitors love exploring the history of the site, admiring the magnificent architecture, and enjoying the stunning views of the surrounding landscape.