A mortal sin, in Catholic theology, is a gravely sinful act, which can lead to damnation.
Mortal Sin(s) may also refer to:
Film and television The Mortal Sin, an American lost 1917 silent film Mortal Sin (film), a 1970 Brazilian film Mortal Sin, a 1977 film featuring Paul Naschy Mortal Sins, a 1989 film featuring Debrah Farentino and James Saito Mortal Sins, a 1992 film featuring Lisa Vultaggio and Christopher Reeve "Mortal Sins" (Highlander), a 1995 television episode
Other uses Mortal Sin (band), an Australian metal band Mortal Sins, a 2009 novel in the World of the Lupi series by Eileen Wilks Mortal Sins, a 2013 book by Michael D'Antonio