A distinctive feature of Babylonian onomastics in the first millennium BCE is the use of family names at most cities by a segment of the population that can be described as the urban notable class. These family names are common and the conventions for their usage are well established in the abundant legal and administrative tablets that date from the so-called 'long sixth century': the period stretching from Nabopolassar's first regnal year in 625 to Xerxes I's suppression of the Babylonian revolts in 484 (Jursa et al. 2010, 2-5). The use of family names emerged during the preceding eighth and seventh centuries, and the antecedents of some families and family names can be traced even further back in time to the early first millennium or even the latter part of the second millennium. Furthermore, some of these families persisted into the latter half of the first millennium BCE, as demonstrated by the continued presence of family names in Seleucid-era tablets.Usage of family names at all times appears to have been restricted. Non-Babylonians never had family names, and only Babylonians of a certain social status were identified in texts with family names. Where the line of social demarcation lay is difficult to determine. Slaves and people of servile status, such as temple oblates, did not have family names, but neither did some men who had sufficient wealth to purchase land associated with the temple (Nielsen 2015b, 101), suggesting that an element of familial pedigree was involved. One could not simply adopt a family name. As a consequence, an understanding of the norms of family-name usage and an ability to identify them in Neo-Babylonian texts is essential for comprehending how individuals from the urban notable class functioned politically, economically, and socially.After a discussion of the origins of family names in Babylonian society, we will present an overview of the types of family names that were in existence and then outline the different ways in which family names were recorded in texts, before concluding with some comments on the geographical distribution of family names throughout Babylonia.