The Andaikhudag Formation, in older literature referred to as Unduruh Formation or Ondorukhaa Formation, is an Early Cretaceous (Hauterivian to Barremian) geologic formation in Mongolia.

[1] Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.

[2] The following fossils have been reported from the lacustrine shales and secondary sandstones of the formation:[1]