斋戒，是伊斯兰教的五功之一。完成斋戒的条件是在赖买丹月（رمضان，Ramadan，伊斯兰历的九月）太阳出现的时段内禁止饮食。

古兰经2章185节说：「……害病或旅行的人，当依所缺的日数补斋。真主要你们便利，不要你们困难，……」害病是指生病的人或生理期／怀孕／哺乳的妇女。害病的人等身体恢复正常及旅行者结束旅行后都须补齐欠斋日数。

古兰经2章184节：「……难以斋戒者，当纳罚赎，即以一餐饭，施给一个贫民……」

Sawm (Arabic:صوم‎; plural: صيام ṣiyām) is an Arabic word for fasting regulated by Islamic jurisprudence. In the terminology of Islamic law, sawm means to abstain from eating and drinking during daylight hours. The observance of sawm during the Islamic holy month of Ramadan is one of the Five Pillars of Islam, but is not confined to that month.