Crypto-Christianity is the secret adherence to Christianity, while publicly professing to be another faith; people who practice crypto-Christianity are referred to as "crypto-Christians". In places and time periods where Christians were persecuted or Christianity was outlawed, instances of crypto-Christianity have surfaced.

In Islam, Taqiyya is a precautionary dissimulation or denial of religious belief and practice. Generally, taqiyya is the action of committing a sinful act for a pious goal.