The Nimrud Slab, also known as the Calah Orthostat Slab, is the top half of a "summary inscription" of the reign of Adad-nirari III (811 to 783 BC) discovered in 1854 by William Loftus in his excavations at Nimrud on behalf of the Assyrian Excavation Fund.

[1] It is the best known of the inscriptions of Adad-nirari III,[2] since it includes a description of early Assyrian conquests in Syria and Palestine.

The original slab was temporarily lost after it was thought to have been left behind in Nimrud.

Excavations by Iraqi archaeologist Muzahim Hussein in 1993 relocated the slab in the so-called "Upper Chambers" area of the Nimurd citadel, first excavated by Austen Henry Layard, and Dr. Ali Yassin Ahmad published the inscription in the Iraqi journal Sumer (LI nos.

Excavations by a University of Pennsylvania Museum team led by American archaeologist Dr. Michael Danti in the "Upper Chambers," more properly the Palace of King Adad Nerari III, re-examined this area in 2022.