The Hasandong Formation (Korean: 하산동층; Hanja: 霞山洞層; RR: Hasandong-cheung) is an Early Cretaceous (Aptian to Albian) geologic formation in South Korea.

[1] Dinosaur remains have been discovered from this formation, though no genus is considered valid as of 2016.

[2] Other reptiles from the formation include the adocid turtle Proadocus and possibly the pterosaur Dsungaripterus.

[27] Tracks of theropods, sauropods and ornithopods have been discovered from the formation.

The assemblage of plant fossils from the Hasandong represents the 'mixed' type of Tetori-type and Ryoseki-type flora.