Al Abbas Mosque, Religious mausoleum in Karbala District, Iraq.

The Al-Abbas Shrine in Karbala is the mausoleum of Abbas ibn Ali, half-brother of Imam Husayn. At its center, the tomb lies within an ornate wooden sarcophagus and a silver zarih made by Isfahan craftsmen in 1965–1966, using about 400,000 mithqals of silver and 8,000 of gold. Four symmetrical arcaded halls (riwaqs) with mirror-mosaic walls surround the tomb, and a large gilded dome rises above it. Two minarets flank the southern iwan, whose enameled golden door was also made in Isfahan.

The Banu Asad tribe first marked Abbas's grave with a prominent tomb so its location would not be lost. Mukhtar al-Thaqafi erected the first known structure after his uprising; the Abbasid caliph Harun al-Rashid ordered its demolition in 170 AH (786–787 CE). The present core was built under the Buyid ruler Adud al-Dawla, begun in 367 AH (977–978 CE) and completed in 372 AH (982–983 CE).

Abbas ibn Ali, called Abu al-Fadl, was Husayn's flag-bearer and caravan chief at Karbala, and pilgrims remember his ride to the Euphrates for water. Shah Ismail I donated twelve golden lamps named for the Twelve Imams and hired attendants to keep them lit; their descendants, known as Al Qandil, still live in Karbala.

The shrine stands about 378 metres northeast of the Imam Husayn Shrine, and the two are linked by the large plaza called Bayn al-Haramayn, so most pilgrims walk between them on foot. The tomb sits at the centre of a square courtyard ringed by arcaded halls, with the southern iwan and its golden door as the main approach. Crowds peak during Muharram and the Arba'in pilgrimage, when millions arrive.

Abbas was killed near the Alqamah Canal while trying to bring water from the Euphrates to Husayn's camp, and his body stayed where he fell because fighting had intensified. Over the centuries the Euphrates changed course and now flows around the shrine, giving rise to the saying that the Euphrates has come to Abbas.