Ripley was born in 2092 in Olympia, Luna. She had a daughter, Amanda Ripley MacLaren, and no other descendants (not counting her clone in Alien Resurrection).
In 2122, Ripley was employed as Warrant Officer (Ident Number W5645022460H) for the Weyland-Yutani corporation, working on the USCSS Nostromo, which was towing massive quantities of raw ore to Earth from Thedus.
Along with the rest of the crew, she was awakened 10 months prematurely from hypersleep by Mother, the ship's computer, to answer a curious transmission received from moon LV-426. Upon landing, Executive Officer Kane, Captain Dallas, and Navigator Lambert disembarked and investigated the source of the transmission a derelict alien space craft. While investigating the derelict craft, an alien parasite attached itself to Executive Officer Kane.
Ripley initially refused to allow the landing party back onto the ship after they were injured, citing quarantine regulations. Her order was ignored by Science Officer Ash, whom she began to distrust more and more as time went on. The bypassing of quarantine had serious consequences when an extraterrestrial larva or embryo of some kind deposited by the "facehugger" that attacked Kane matured and erupted from his chest. Kane was killed by this alien birth, and the creature quickly took to preying upon the rest of the crew.
Following the presumed death of Dallas, Ripley became the Nostromo's commanding officer, and learned from Mother the final piece of the puzzle: Special Order 937, a secret Company policy to study the very creature that was stalking them at the expense of their lives. With the crew around her dwindling just as quickly as the creature seemed to be growing, Ripley began the vessel's self-destruct sequence. The Nostromo, the cooling rods removed from its reactor, melted down and exploded violently, moments after Ripley (in the escape ship Narcissus) reached safety. She was expecting to be rescued within a few weeks, but she and her cat Jones would drift "right through the core systems" and spend the next 57 years in hypersleep. Ripley's only daughter, Amanda, died at the age of 66, just two years before Ripley would be found and awoken from hypersleep. A photograph shown in a brief clip in the special edition of Aliens (1986) has her date of death listed as "12.23.20", but a later line from Carter Burke places the events of the same film 57 years later (2179).
After her subsequent rescue by a salvage crew, Ripley was made a Lieutenant and reluctantly returned to LV-426 with a team of United States Colonial Marines to rescue the colonists of Hadley's Hope, and basically became the unit's de facto leader after most of the marines were killed. Ripley escaped with one colonist, an injured marine, half of an android, and (unbeknownst to her) a super-facehugger (Emperess class : Multi-embryo producing organism, awakened only when the death of the current Alien Queen is unavoidable). She subsequently found herself marooned on Fiorina "Fury" 161, an outer-veil mineral ore refinery and correctional facility, where she died while trying to prevent Weyland-Yutani from getting its hands on the alien queen that was inside of her.
Various clones of Ellen Ripley were later created by the military for the purpose of experimentation with the alien. (See Alien: Resurrection (1997)) The protagonist clone, Ellen Ripley 8 has traces of xenomorph genes inside of her that gave her superior strength, endurance, caustic blood and the ability to sense and communicate with the creatures. Due to some form of "genetic memory" derived from the aliens the Ripley clone could learn at an extremely rapid rate and recall some of the original's memories and personality. The clone was not an exact mental duplicate as she was more violent, fatalistic and sadistic than the original. She also had a mild empathy for the xenomorphs and antipathy for humans.
Ripley 8 discovered the seven experimental, deformed clone Ripleys in a military lab. At the pleading of the last surviving one (Ripley 7) she incinerated the lab and all the clones with a flamethrower.