The Lourinhã Formation is a fossil rich geological formation in western Portugal, named for the municipality of Lourinhã. The formation is mostly Late Jurassic in age (Kimmeridgian/Tithonian), with the top of the formation extending into the earliest Cretaceous (Berriasian). It is notable for containing a fauna especially similar to that of the Morrison Formation in the United States and a lesser extent to the Tendaguru Formation in Tanzania. There are also similarities to the nearby Villar del Arzobispo Formation and Alcobaça Formation. The stratigraphy of the formation and the basin in general is complex and controversial, with the constituent member beds belonging to the formation varying between different authors.

Lourinhã is a municipality in the District of Lisbon, in the Oeste Subregion of Portugal. The population in 2011 was 25,735, in an area of 147.17 km2. The seat of the municipality is the town of Lourinhã, with a population of 8,800 inhabitants.