Abstract: The disclosure relates to systems and methods of identifying mobile devices of users involved in purchase transactions. The system may obtain purchase information that indicates purchases made by users and location information associated with mobile devices that may be potentially associated with the users. The system may identify a mobile device of a user that makes a purchase at a retail establishment by comparing the time of the purchase, as determined from the purchase information, with timestamps of mobile device locations, which may indicate a time that the mobile device was at a given location. In this manner, even if the mobile device of the user is not known in connection with a given purchase transaction, the system may determine a probability that the mobile device belongs to the user based on the time of the purchase transaction and the timestamps of mobile device locations.