Al-Masjid an-Nabawi known in English as The Prophet's Mosque, is a mosque built by the Islamic prophet Muhammad PBUH in the city of Medina in the Al Madinah Province of Saudi Arabia. It was the second mosque built by Prophet Muhammad PBUH in Medina, after Masjid Quba', and is the second largest mosque and second holiest site in Islam, both titles ranking after the Masjid al-Haram in Mecca. It is generally open regardless of date or time, and has only been closed to visitors once in modern times, as Ramadan approached during the 2020 COVID-19 pandemic.

The land of Al-Masjid an-Nabawi belonged to two young orphans, Sahl and Suhayl, and when they came to know that Muhammad wished to acquire their land for the purposes of erecting a mosque, they went to Prphet Muhammad PBUH and offered the land to him as a gift; Prophet Muhammad PBUH insisted on paying a price for the land because they were orphaned children. The price agreed upon was paid by Abu Ayyub al-Ansari, who thus became the endower or donor (waqif) of Al-Masjid an-Nabawi on behalf of, or in favor of, Prophet Muhammad PBUH. Al-Ansari also accommodated Prophet Muhammad PBUH upon his arrival at Medina in 622.

Prophet Muhammad PBUH shared in the construction of the mosque. Originally an open-air building, the mosque served as a community center, a court of law, and a religious school. There was a raised platform or pulpit (minbar) for the people who taught the Quran and for Muhammad to give the Friday sermon (khutbah). Subsequent Islamic rulers greatly expanded and decorated the mosque, naming its walls, doors and minarets after themselves and their forefathers.

After an expansion during the reign of the Umayyad caliph Al-Walid I, it now incorporates the final resting place of Muhammad and the first two Rashidun caliphs Abu Bakr and Umar. One of the most notable features of the site is the Green Dome in the south-east corner of the mosque, originally Aisha's house, where the tomb of Muhammad is located. Many pilgrims who perform the Hajj also go to Medina to visit (Ziyarah) the Green Dome. In 1909, under the reign of Ottoman Sultan Abdul Hamid II, it became the first place in the Arabian Peninsula to be provided with electrical lights. The mosque is under the control of the Custodian of the Two Holy Mosques. The mosque is located at the heart of Medina and is a major pilgrimage site.