Parachuters at the Leagues Cup final on Wednesday night caused a MASSIVE freak-out in Las Vegas ... 'cause people legitimately thought they were aliens!!!
Before Cruz Azul and Tigres UANL faced off for the championship at Sam Boyd Stadium ... members of the U.S. Navy Parachute Team flew down from the sky with pyrotechnics strapped to them.
The problem? Not all Vegas residents knew their plan ... and when they saw the jumpers in the sky -- they thought Mars was attacking!!!
People were freaking out on Twitter for hours ... until UNLV officials confirmed there were no aliens -- just awesome parachuters.