Third-party location-based services are independent of wireless carriers and receive the user location from mobile devices GPS. A major problem in this context is how to prevent service abuse by malicious users who submit false locations by tampering with their phones. This paper presents LINK (Location authentication through Immediate Neighbors Knowledge), a location authentication protocol working independent of wireless carriers, in which nearby users help authenticate each other’s location claims using Bluetooth communication. Simulation results demonstrate that LINK thwarts individual user attacks and a number of colluding users attacks. Experimental results over Android phones show that LINK works well at walking speeds and phone battery is not impacted significantly even for relatively high usage.