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.