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

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