Marduk-bēl-zēri, inscribed in cuneiform as ^dAMAR.UTU.EN.NUMUN^{[i 1][i 2]} or ^mdŠID.EN.[x]^{[i 3]} and meaning 'Marduk (is) lord of descendants (lit. seed)',^[1] was one of the kings of Babylon during the turmoil following the Assyrian invasions of Šamši-Adad V (ca. 824 – 811 BC). He is identified on a Synchronistic King List fragment^{[i 3]} as Marduk-[bēl]-x, which gives his place in the sequence and reigned around the beginning of the 8th century BC. He was a rather obscure monarch and the penultimate predecessor of Erība-Marduk who was to restore order after years of chaos.^[2]

He is known from a single economic text^{[i 1]} from the southern city of Udāni dated to his accession year (MU.SAG.NAM.LUGAL). This city was a satellite cultic center to Uruk, of uncertain location but possibly near Marad, later to be known as Udannu, associated with the deities ^dIGI.DU (the two infernal Nergals) and Bēlet-Eanna (associated with Ištar).^[3] The document records the parts of a chariot including the wagon pole (mašaddu) which had been entrusted by Belšunu, the šangû or chief administrator^[4] of Udāni to the temple of ^dIGI.DU (Igišta, Palil?).^[1] He is tentatively restored to the Dynastic Chronicle^{[i 2]} where he is described as "a soldier" (^lúaga.[úš]) but his circumstances are otherwise unknown.^[5]