Systems and methods are provided for use in identifying synthetic identities. One exemplary method includes receiving a request from a relying party to assess validity of an identity indicated by a user in a network communication between the user and the relying party, where the request includes: identity data associated with the identity indicated by the user, feature data associated with submission of the network communication by the user to the relying party, and a device ID for a communication device associated with the user and used to submit the network communication. The method then includes calculating an assessment metric representative of the validity of the identity indicated by the user based on at least one score derived from the identity data, the feature data, and the device ID, and transmitting the assessment metric to the relying party.