The Selenites (named after the Greek moon goddess Selene) are a race inhabiting the Moon in the 1902 French film A Trip to the Moon. They are the first ever aliens to be portrayed in cinema.
Shortly after arriving on the Moon on a cannon-launched capsule, a group of astronomers are accosted by a Selenite. After a brief struggle, they discover the aliens have a glaring weakness...they explode if struck with a hard object. More Selenites appear, and soon, the astronomers are overwhelmed by their numbers.
Taken captive, the explorers are hauled before the Selenite King. However, one of the group breaks free and kills the king by tossing him to the ground. The men flee, pursued by the other Selenites. The astronomers return to their capsule, which they push over a cliff to fall back to Earth. A Selenite attempts to stop them by grabbing onto the capsule, but is instead taken to Earth.