This paper describes the role of the International Telecommunication Union (ITU) in the registration of satellite and other space systems with a focus on its response to the unprecedented surge of filings related to large satellite constellations. The paper will also discuss the upcoming World Radiocommunication Conference in late 2023 (WRC-23) which will amend the international Radio Regulations, a treaty addressing the use of radio spectrum and orbits, and ITU’s Master International Frequency Register. The paper will compare key elements of the ITU’s Master Register with the Register maintained by the United Nations (UN) Office of Outer Space Affairs pursuant to the Convention on Registration of Objects Launched into Outer Space. Finally, the paper will briefly explore opportunities for increased collaboration between these two UN organizations to address these shared challenges concerning registration of satellites.