A province in the northern part of the Valencian Community, Spain. Castellón is bordered by the provinces of Valencia, Teruel and Tarragona. The eastern side of Castellón is bordered by the Mediterranean Sea.

In 2008, Castellón had a population of approximately 602,301 inhabitants. Trends from 2002 indicate that most people live along the coastline of Castellón. Others live in the provincial capital, Castelló de La Plana, and its surrounding metropolitan areas.

Two languages are spoken in Castellón: Spanish, and the local Valencian dialect.