This article publishes a royal inscription preserved on a clay tablet housed in the Istanbul Archaeological Museums. The inscription, which was intended for display on a stele, commemorates a royal grant of tax exemptions to nine Babylonian cities and presents the royal protagonist as a second Ḫammu-rāpi. The name and titulary of the king in question are not preserved, and the attribution of the inscription is accordingly uncertain. Following Jean-Vincent Scheil’s attribution of the text already in 1902, the study that accompanies an edition of the text argues that it should be attributed to Nabonidus, king of Babylon 556–539 BC, and explores its historical significance in this context.