Olocau del Rey is a municipality in Spain, located in the province of Castellón within the Valencian Community. It lies in the eastern part of the country, in the inland comarca of Els Ports, near the border with the neighbouring region of Aragon.
The town is one of the smaller and more remote settlements of the Castellón interior, set in a mountainous area characterised by rugged terrain and a sparse population. Its historic centre preserves a traditional layout typical of the region, with narrow streets and stone buildings clustered around the parish church.
Like much of the surrounding Maestrazgo and Els Ports area, Olocau del Rey is known for its quiet rural setting and its medieval heritage, including the remains of a castle that once formed part of the defensive network along the historic frontier between the kingdoms of Valencia and Aragon.