The Hasandong Formation () is an Early Cretaceous geologic formation in South Korea. It has been dated to the Aptian to possibly the earliest Albian stage. Lee et al. (2018) estimated the maximum depositional age of the formation at 118.0â¯ñâ¯2.6â¯Ma, and suggested that the overlying Jinju Formation likely had a maximum depositional age of 112.4 ñâ¯1.3â¯Ma. Chae et al. (2026) examined the upper part of the Hasandong Formation on Yusu-ri, Jinju and on Jangguseom Island of Jungpyeong-ri, Hadong, and estimated the maximum depositional age of the upper part of the formation on each site at 116.9 ñ 1.5 Ma and 113.4 ñâ¯1.4â¯Ma respectively. Fossils including dinosaurs, turtles and pterosaurs are known from this formation.
Few fragments of insects have been discovered from the formation.
Ostracod carapaces have been discovered from the formation.
Shell fragments of testudines have been discovered.
Several teeth remain have been reported but are not assigned to the specific clade.
Several indeterminate theropod teeth remains have been reported.
Unnamed dinosaur egg fossils have been reported.
Tracks of theropods, sauropods and ornithopods have been discovered from the formation. Possible amphibian tracks are also known.
Consists of 6 genera and 9 species. The assemblage of plant fossils from the Hasandong represents the 'mixed' type of Tetori-type and Ryoseki-type flora.