Buffy Summers, played by Sarah Michelle Gellar, was vampires' worst nightmare in the beloved TV series "Buffy the Vampire Slayer."
From 20th century fox television
Brie Larson is set to star as Carol Danvers / Captain Marvel in the forthcoming "Captain Marvel" film due in theaters in 2019. She will join a group of kick ass women in superhero and sci-fi films which include....
Gal Gadot's Wonder Woman first made an appearance in the 2016 film "Batman v Superman: Dawn of Justice." Her 2017 solo movie broke a box-office record for most money made by a film directed by a woman on its opening weekend.
Clay Enos/Warner Bros.
Charlize Theron kicked butt and looked fabulous while doing it as an undercover MI6 agent in "Atomic Blonde." She was strong, smart and beyond fierce in the role.
Daisy Ridley portrays Rey, a young scavenger on the desert planet of Jakku in "Star Wars: Episode VII - The Force Awakens."
Former "Glee" star Melissa Benoist (also seen in the Oscar-nominated "Whiplash") plays Supergirl in the CBS series of the same name.
Blasting her way out of the Death Star, we knew fairly quickly that Leia was not one to be trifled with in the "Star Wars" films. Carrie Fisher played the role.
Krysten Ritter stars as "Jessica Jones" in the Netflix series based on Marvel Comics' "Alias," about a semi-retired superhero-turned-private eye.
Jennifer Lawrence is back as archer and freedom fighter Katniss Everdeen in "The Hunger Games: Mockingjay, Part 1" and coming soon, the final film, "Part 2."
Zoe Saldana stars in not one but three major sci-fi movie franchises. She's Lt. Nyota Uhura in the rebooted "Star Trek" movies, stars as former assassin Gamora in the Marvel hit "Guardians of the Galaxy" and is Neytiri in "Avatar" and its planned sequels.
Marvel/Twentieth Century Fox
Nichelle Nichols played Lt. Uhura, the communications officer on the Starship Enterprise, in the original "Star Trek" TV series and films. In the recent movie reboots, her role was played by Zoe Saldana.
CBS/Paramount Television/getty images
Margot Robbie portrayed Batman villain (and the Joker's paramour) Harley Quinn in the eagerly awaited film "Suicide Squad."
Set in the post-World War II years, the new series "Marvel's Agent Carter" follows the continuing adventures of Peggy Carter, after the presumed death of her boyfriend Steve Rogers (a.k.a. Captain America).
Scarlett Johansson stole the movie in her first scene in "The Avengers" -- not an easy thing to do. Black Widow was pretty kickass in the film.
"Lucy" seems to have boosted Johansson's action movie cred. The actress is reportedly starring in the live-action remake of "Ghost In The Shell."
Courtesy Universal Pictures
Lucy Lawless found fame on TV as the force of nature that was "Xena, Warrior Princess."
YouTube/ Renaissance Pictures
Sigourney Weaver faced off with aliens not once, but four times in the "Alien" films and became the very model of the modern sci-fi heroine.
From Twentieth Century Fox
Linda Hamilton (pictured) was the best known Sarah, but Emilia Clarke took on the Terminator in the 2015 reboot.
TriStar Pictures/Lightstorm Entertainmen
Carrie-Anne Moss' Trinity was the first main character we saw in the "Matrix" and immediately, we were hooked.
Tatiana Maslany's "clone club" brings new meaning to the term "girl power" on the critically-acclaimed BBC America series "Orphan Black." Maslany plays Sarah Manning on the show.
Steve Wilkie for BBC America
She may not have "wanted to believe" like her partner Fox Mulder, but Gillian Anderson as Scully on "The X-Files" was one of the best sci-fi characters of the past 20 years.
20th Century Fox /Everett Collection
It's hard to choose a favorite Lois as there's been so many over the years, but we'll go with Margot Kidder's tough as nails reporter from the Christopher Reeve "Superman" movie series.
From Warner Bros.
They switched genders on us with this character in the 2000s reboot, and casting Katee Sackhoff as Starbuck in "Battlestar Galactica" was a stroke of genius.
From Sci-Fi Channel
We didn't even see her face but when she used her katana to slice through zombies at the end of season two, we knew we really liked Michonne, actress Danai Gurira, from "The Walking Dead" right away.
Emma Watson's Hermione Granger in the "Harry Potter" movies always knew just the right spell to get out of any situation.