Father Lankester Merrin is a fictional title character in the 1971 novel The Exorcist and one of the main protagonists in its 1973 film adaptation.

Merrin, an elderly Irish priest and paleontologist on an archeological dig in Iraq, finds images of the demon Pazuzu and subsequently experiences other unusual phenomena.

Merrin does not appear again until much later in the novel, when he joins the protagonist, Father Damien Karras, in Washington, D.C., to exorcise the demon from the body of a young girl (Regan MacNeil).

Merrin is loosely based on the British archaeologist Gerald Lankester Harding,[1] though in the film he is played by Max von Sydow with a noticeably Irish accent.

The character of Merrin reappears in the sequel Exorcist II: The Heretic (1977), in extended flashbacks detailing an exorcism he performed in Africa following the Second World War.