The Sinuiju Formation is a geologic formation in North Korea. Formerly of uncertain age, it is now thought to be Early Cretaceous. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation. Compression fossils of insects are also known from the formation. Several bird fossils are found in this formation, including a very large enantiornithine specimen with a 5 cm (2.0 in) long tibia and a 3.5 cm (1.4 in) long pygostyle. Amphibian fossils, including frogs and lissamphibians, have also been found here.