Larymna (Greek: Λάρυμνα) is a port town in Phthiotis, Greece.

Since the 2011 local government reform, it is a part of the municipality Lokroi, of which it is a community.

The modern years, Larymna was a small village known also with the name Kastri.

The name Kastri derives from the well-kept ancient wall in the coast.

Larymna developed after the foundation of mining and metallurgical industry LARCO, opposite Larymna's port.