In some religions, an unclean animal is an animal whose consumption or handling is taboo. According to these religions, persons who handle such animals may need to ritually purify themselves to get rid of their uncleanliness.

According to the Acts of the Apostles, chapter 10, Saint Peter had a vision of a vessel full of animals being lowered from heaven. A voice from heaven told Peter to kill and eat, but since the vessel contained unclean animals, Peter declined. The command was repeated two more times, along with the voice saying, "What God hath made clean, that call not thou common" and then the vessel was taken back to heaven.