Sister Mary Explains It All is a 2001 satirical dark comedy film written by Christopher Durang and directed by Marshall Brickman. The film, based upon Durang's 1979 play Sister Mary Ignatius Explains It All For You, and starring Diane Keaton in the title role, premiered on the Showtime network.

Plot

Sister Mary (Diane Keaton) is an authoritarian Catholic nun who teaches children. Her teaching is heavily influenced by her fanatical beliefs. Four of her former pupils, Gary (Brian Benben), Aloysius (Wallace Langham), Angela (Laura San Giacomo) and Philomena (Jennifer Tilly), return to the school to show her how deeply her strict views on faith and sin have affected their lives.