The Oriental cuckoo or Horsfields cuckoo (Cuculus optatus) is a bird belonging to the genus Cuculus in the cuckoo family Cuculidae. It was formerly classified as a subspecies of the Himalayan cuckoo (C. saturatus) with the name Oriental cuckoo used for the combined species. Differences in voice and size suggest that they should be treated as a separate species. The binomial name Cuculus horsfieldi has often been used instead of Cuculus optatus but is now usually considered to be a junior synonym.