Embodiments of Vehicle-to-everything (V2X) communications authentication are described. In some embodiments, a user equipment (UE) configured V2X communication and configured to operate within a fifth-generation system (5GS) and/or a combined 5GS and fourth-generation system (4GS) can encode a V2X capability indication in a request message for transmission to a network entity, such as a Access and Mobility Management Function (AMF). The V2X capability indication can indicate a capability of the UE for V2X communication over a PC5 reference point, and the request message can further include an indication of a Radio Access Technology (RAT). In some embodiments, the AMF can determine whether the UE is authorized to use the V2X communications over the PC5 reference point, and whether the UE is authorized to use the RAT indicated in the request message. Accordingly, the AMF can transmit a V2X services authorization to a next generation radio access network (NG-RAN).