Bad faith is double mindedness or double heartedness in duplicity, fraud, or deception.

Bad faith may also refer to:

• Insurance bad faith, a legal term of art
• Bad faith (existentialism), a philosophical concept used by existentialist philosophers Jean-Paul Sartre and Simone de Beauvoir
• Bad Faith (novel), a 2008 novel by Gillian Phillip
• "Bad Faith" (Law & Order), an episode of the TV series Law & Order
• Bad Faith, a fictional rock band in the New Tricks TV series episode "Loyalties and Royalties"
• "Assume bad faith" an unofficial principle/behavioral guideline of the English Wikipedia.

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