Montalto di Castro is a comune, or municipality, situated in the province of Viterbo within the Lazio region of central Italy. It is geographically positioned approximately 90 kilometres northwest of the capital city, Rome, and about 40 kilometres west of Viterbo.
The town serves as a local administrative center within its province. Its location in the Lazio region places it in a prominent area of the Italian peninsula known for its historical and geographical diversity.