Species is a 1995 science fiction thriller. It stars Natasha Henstridge, Ben Kingsley, Michael Madsen, Forest Whitaker, Alfred Molina and Marg Helgenberger.

This film produced one theatrical sequel in 1998, Species II. Natasha Henstridge, Michael Madsen, and Marg Helgenberger all returned. It was followed by the direct-to-video Species III in 2004 and "Species: Quattro" in 2007.

The movie is about a group of scientists who try to track down and trap a killer alien before she successfully mates with a human male.

The alien is the result of the SETI program, (Search for Extra Terrestrial Intelligence). Scientists receive transmissions from an alien source on how to create endless fuel effortlessly. They also receive information about an alien DNA along with instructions on how to splice it with human DNA. Thinking it might be as beneficial as the fuel source, they splice the DNA. The effort produces a girl (named Sil) who looks normal (human) but develops into a 12-year old in 3 weeks. She is incredibly strong and intelligent with amazing regenerative powers. Considering her to be a threat, the scientists try to destroy her but she breaks out of her containment cell and escapes out into the world. The government assembles a team composed of Dr. Stephen Arden, an anthropologist (played by Alfred Molina), Dr. Laura Baker, a molecular biologist (played by Marg Helgenberger), Dan Smithson, an empath (played by Forest Whitaker) and Press Lennox, an assassin (played by Michael Madsen) to track and destroy Sil.

Sil matures rapidly into an adult (played by Henstridge) in her early twenties. This makes tracking her extremely difficult. The scientists fear she may mate with human males and produce offspring that could eliminate the human race. Sil does not have any inhibitions when it comes to killing people who get in her way and wants to produce an offspring as soon as possible. She eventually copulates with the anthropologist from the tracking team, whom she then kills. The tracking team then follow her into the sewers and a cave where she and her offspring are destroyed. The last scenes details a rat chewing on one of Sil's severed tentacles and it starts to mutate into a vicious beast. It attacks another rat.

The creature was created and designed by Swiss artist H. R. Giger who also created the famous Alien creature. The ghost train was also his design which he demanded to be in the final film.

The comic adaptation, from Titan Books, incuded many scenes that was not in the film. These included:

The film originally began with scientists discovering the alien signal in space and Fitch having a meeting with the government to begin this experiment of combing alien DNA to a human host. A shot of the scientists discovering the signal was in the theatrical trailer. The scene with Fitch's introduction was cut out as the sequence was explained to the team consisting of Press, Laura, Dan and Steve later in the final film. There were also publicity stills of Fitch with the 2-week old Sil in some press kits for the film that did not make the cut.

Sil's dreams were more intense and organic involving mutant worms and acid. Due to budgetary reasons, this was never filmed.

As in the novel, the interpretation of Sil's rejection to a man is a green mist surrounding the host that was not apparent in the film.

Sil's fantasy dream of her making love to Press was hinted in the film but not shown in its entirety. The two make love in her dream and Press mutates into a creature with spikes penetrating Sil's chest, causing her to die. She wakes up from her nightmare.

In the adaptation, Sil's death is not as dramatic as in the film which involved fire and tension. In the comics, she gets blown to bits from Press's cannon blaster and is splatted all over the cavern. In the film she supposedly dies from multiple gun shots and falls into the vat of fire but returns to kill Dan only to have her head blown off by Press's cannon blaster and fall into the vat of flames.

In the alternative ending, Press sits with Laura on an embankment and mentions how he respected her with human qualities. They then kiss and hug each other with relief that they survived. Laura poses the question whether Sil's agression was part of her alien biology, or if it came from the human part of her DNA? Laura reminds Press that humans are a predatory species (as indicated by their binocular vision, a point raised earlier in the film). This was featured on the Special Edition DVD and was shot at a pier near an ice cream shop. The ending was re-shot by Boss films under the direction of Roger Donaldson involving the mutated rat puppet.

The main character from the film is mentioned in the 2001 music track "Love Me Madly" by The Human League's album "Secrets": "You're like the woman out of Species - I think I'm going to go to pieces."

Written by Yvonne Navarro, from the original screenplay the book gives several in depth details about the characters not seen in the film, such as Sil's ability to visualise odors and determine harmful substances from edible items by the colour. Gas appears black, Food appears pink, an unhealthy potential mate appears to give off green fumes. Other character details include Press's background in tracking down AWOL soldiers as well as the process of decoding the alien signal. Although no clues are given as to its origin, it is mentioned that the message was somehow routed through several black holes to mask its point of origin. Parts of these extra scenes and details are shown in the comic book adaptation by Titan Books. There is also a novelization by Yvonne Navarro for Species II which follows the film's original screenplay with added scenes.