Agnes of God is a 1979 play by American playwright John Pielmeier which tells the story of a novice nun who gives birth and insists that the child was the result of a virgin conception. A psychiatrist and the mother superior of the convent clash during the resulting investigation. The title is a pun on the Latin phrase Agnus Dei (Lamb of God).

The stage play concerns three main characters: Martha, the psychiatrist; the Mother Superior; and Agnes, the novice. There are no other characters on stage. All three roles are considered demanding for the actors playing them.[1] Martha covers the full gamut of emotion during the play, from nurturer to antagonist, from hard nosed court psychiatrist and atheist to faith-searching healer. She is always on stage and has only three small respites from monologues or dialogue while Agnes and the Mother Superior enact flashbacks to events at the convent. The Mother Superior must expound the possibilities of miracles while recognizing the realities of today's world. Agnes is a beautiful but tormented soul whose abusive upbringing has affected her ability to think rationally.