What cinematic universe includes the characters Ellen Ripley and the Xenomorphs?

The Alien universe began with Ridley Scott's 1979 film of the same name, with Sigourney Weaver as Ellen Ripley facing off against a deadly extraterrestrial creature known as a Xenomorph. The franchise expanded with sequels, prequels ('Prometheus', 'Alien: Covenant'), crossovers with Predator, comics, novels and video games, exploring themes such as motherhood, corporatocracy and the artificial creation of life.