It is frequently asserted by scholars that both Josephus and the rabbis know of the conversion to Judaism of the royal house of Adiabene. This paper argues that this is far from clear in Tannaitic sources. These sources do hint at Helena and Monobaz’s provenance from outside the Land of Israel, but they never mention that they were not born Jewish. If they know of the conversion, it is not a factor they choose to highlight in their assessment of these figures. Queen Helena and her son Monobaz appear several times in rabbinic literature, starting in the Mishnah and Tosefta. Only one later source (Genesis Rabbah 46:10) directly mentions the conversion of either party. This story, however, has no clear relationship to the earlier sources which mention Helena and Monobaz. This narrative was likely incorporated separately from an external source (some scholars have suggested Josephus himself, an intermediary, or a shared source) and therefore cannot be taken as evidence that the earlier, inner-rabbinic sources have any knowledge of the conversion nor that they mean their depiction of Helena and Monobaz as a reflection on their status as converts.
