‘Iṣmah or ‘Isma (Arabic: عِصْمَة‎) is the concept of infallibility or "divinely bestowed freedom from error and sin" in Islam.Muslims believe that Muhammad and other prophets in Islam possessed ‘iṣmah. Twelver and Ismaili Shia Muslims also attribute the quality to Imāms and Fatima Zahra, daughter of Muhammad. Zaidi Shia however, do not attribute ‘ismah to the Imāms.

The concept that Islam had sinless messenger arises from the Quran. It clearly stated in the first four verse of the 53rd Chapter. The verses clearly state that the prophet does not lie nor is he led astray. The third verse says that he never speaks out of his own inclination. The fourth verse states that what ever he speaks is inspired from God.

The doctrine has been rejected by some, such as the Kharijites, who point to the second ayah in the Surah of Al-Fath, in which God says to Muhammad that he will; "forgive thee thy faults of the past and those to follow". The Qur'an further states that Muhammad's words are only true and infallible insofar as they communicate the Qur'an itself, and that outside the Qur'an, Muhammad's words may be at fault.