Lias may refer to:
- In geology:
- The Lias Group, a group in the stratigraphy of Great Britain, formed during the Late Triassic to Early Jurassic epochs. It includes the Blue Lias and White Lias. The Lias facies is found in large parts of Europe
- The German Lias, a stratigraphic term that today is used solely for lithostratigraphic units from the Lower Jurassic
- In older literature, Lias was also used as a synonym for the Early Jurassic epoch of the geologic timescale
- Lias (journal), title of the Journal of Early Modern Intellectual Culture and its Sources
- Lias (troll), a troll drummer in the book Soul Music by Terry Pratchett
- Lias, Gers, a commune of the Gers département in France
- Lias De Lange, a member of South African band The Narrow
- Lias (courtesan), an ancient Greek courtesan, who charged 1,000 drachmas for a single night
- Laboratoire d'Informatique et d'Automatique pour les Systèmes (LIAS), a French laboratory situated in Poitiers