The disclosed computer-implemented method for using vehicles as information sources for knowledge-based authentication may include (1) identifying a vehicle belonging to a user who is attempting to authenticate with an identity-verification authority, (2) acquiring analytic information about the vehicle, (3) generating, by analyzing the analytic information about the vehicle, at least one authentication question, where the correct response to the authentication question requires knowledge about the vehicle, (4) presenting the authentication question to the user, and (5) authenticating the identity of the user based on the user responding correctly to the authentication question. Various other methods, systems, and computer-readable media are also disclosed.