Ghadir Khumm refers both to the gathering of Muslims for Muhammad's sermon and its location, which was a pond (Arabic: غَدِير, romanized: ghadir) fed by a nearby spring in a wadi known as Khumm, situated between the cities of Mecca and Medina. The pond was located near the settlement of al-Juhfa, a strategic trijunction where routes from Medina, Egypt, and Iraq intersected.

The word khumm (Arabic: خُم) has been translated as 'deceiver', and the valley was so named because the water of its pond was saline and unfit for consumption. At the time of the event, the original inhabitants of the region, namely, the Banu Khuza'a and the Banu Kinana tribes, had already abandoned the area due to its poor pasturage and harsh climate.[ Before Muhammad's address there, the location was likely never used as a caravan stop. In Shia sources, the harsh environment of Ghadir Khumm is seen as emphasizing the urgency of Muhammad's divine task as he sought the largest audience for his address before the pilgrims parted ways.

The Ghadīr Khumm (Arabic: غَدِير خُم) was a gathering of Muslims to attend a sermon delivered by the Islamic prophet Muhammad on 16 March 632 CE. The gathering is said to have taken place by the ghadir (Arabic: غَدِير, lit. 'pool') in the wadi (Arabic: وداع, lit. 'valley') of Khumm, located near the then settlement of al-Juhfa on the path between Mecca and Medina, where Muhammad halted the large caravan of Muslims who had accompanied him in the Farewell Pilgrimage, his only Hajj ritual.

In the sermon, made shortly before his death in June 632, Muhammad made a declaration in favor of Ali ibn Abi Talib, his cousin and son-in-law, by saying: "He whose mawla I am, Ali is his mawla" (Arabic: من كنت مولاه فهذا على مولاه). Mawla (Arabic: مولاه) is a polysemous Arabic word, which can mean 'patron', 'master', 'leader', or 'friend', depending on its context. Shi'a Muslims believe this sermon to be a clear designation of Ali to lead the Muslim community after Muhammad and celebrate the anniversary of the event as Eid al-Ghadir. The Sunni community meanwhile regards the declaration as a simple affirmation of Muhammad's esteem for Ali.