The disclosed computer-implemented method for detecting illegitimate devices on wireless networks may include (1) generating a fake network identification string that uniquely identifies a fake wireless network, (2) transmitting a request to connect to the fake wireless network, (3) receiving, in response to the request, a response from a network device that indicates the fake wireless network is available, and (4) determining, based on receiving the response that indicates the fake wireless network is available, that the network device is illegitimate. Various other methods, systems, and computer-readable media are also disclosed.