In H.G. Wells' 'The War of the Worlds', Martians invade Earth. The novel imagines intelligent beings from Mars arriving in mechanical fighting machines and attacking late-Victorian England.
Wells published the story in 1898, during a period when Mars was widely discussed as a possibly inhabited world. The invaders land in cylinders near Woking, Surrey, and use heat-rays and poisonous black smoke against human resistance. Their technology makes them appear almost unstoppable.
The novel is more than an alien-invasion adventure. Wells uses the invasion to reverse the logic of empire: technologically superior outsiders treat humans as helpless subjects, echoing the violence European imperial powers inflicted on other peoples. The narrator also reflects on humanity's vulnerability and arrogance.
“Martians” is the canonical quiz answer. “Aliens” is broadly descriptive, but it is less specific; Lunarians and Selenites refer to beings associated with the Moon, not the invaders in Wells's novel.