A donkey (Equus asinus asinus) was a domesticated animal native to Earth. It was similar to a horse.
The Guardian of Forever showed a scene depicting Humans riding camels and donkeys in an Egyptian plateau to the crew of the USS Enterprise in 2267. (TOS: "The City on the Edge of Forever")
Nick Bottom, a character from William Shakespeare's play A Midsummer Night's Dream, was known for having his head turned into that of a donkey by the fairy Puck. Bottom's transformation was depicted in the painting Titania, Bottom and the Fairies, which was found in Captain Picard's edition of The Globe Illustrated Shakespeare: The Complete Works. (TNG: "The Offspring")
The holographic Giuseppina Pentangeli claimed that The Doctor was "lagging behind like a tired donkey" during their performance of the duet "O, soave fanciulla" in 2373. (VOY: "The Swarm")