In Contra, the player controls one of two armed military commandos named Bill "Mad Dog" Rizer and Lance "Scorpion" Bean, who are sent on a mission to neutralize a terrorist group called the Red Falcon Organization that is planning to take over the Earth. Details of the game's setting varies between supplementary materials: the Japanese versions sets the game in the year 2633 on the fictional "Galuga archipelago" near New Zealand, whereas the manual for the American NES version sets the game during the present in an unnamed South American island. The American storyline also changes the identity of "Red Falcon" from being the name of a terrorist organization to the name of an alien entity. Inspired by the movie Aliens.

Home computers

Under license from Konami, Ocean Software produced ports of Contra under the title of Gryzor for the ZX Spectrum, Commodore 64, and Amstrad CPC, which were released in Europe in 1988. An IBM PC version was developed by Banana Productions and released in North America. This version was released in Europe under the Gryzor name. Ocean's ports were patterned after the original arcade version of the game. The Commodore 64 version was released in North America under the Contra title.

The cover illustration of Ocean's Gryzor ports by Bob Wakelin was inspired by different poses of actor Arnold Schwarzenegger from the film Predator. The illustration was later used for the American cover art of the NES version and the Japanese back cover of the MSX2 version.

Nintendo Famicom/Nintendo Entertainment System

Konami produced its own home version of Contra for the Nintendo Famicom/Nintendo Entertainment System, which was released in February 1988 in Japan and North America. The PAL version, titled Probotector, was released in December 28, 1990.

The NES version of Contra differs from the arcade game in a few ways. All ten stages from the arcade version are present, although the "core" segments are no longer individual stages but boss battles that occur at the end of each base stage, reducing the total number of stages to eight. The base stages themselves were also made into linear levels instead of their original maze-like structure (resulting in the removal of the map display) and the time limit was removed as well. The rest of the game's stages were also modified with the addition of more traps (such as surfacing spiked walls, mortar launchers, and bottomless pits). The design of the Area 3 boss (originally Area 4 in the arcade version) was changed as well.

All six power-ups from the arcade version are present, with the Machine Gun and the Laser Rifle now represented by letter-based Falcon icons (an "M" and an "L" respectively) like the other four power-ups. A seventh power-up is also introduced called the "Special", which destroys all on-screen enemies once picked up. It is represented by an unmarked Falcon icon. Unlike the arcade version, the flying capsules appear regardless of which weapon the player is using.

The NES version of Contra was one of the earliest games to use the Konami Code, which originated with the NES version of Gradius. Inputting the code (entirely as the screen scrolls, or entirely after the screen is done scrolling) on the title screen before starting the game will grant each player thirty lives each time they start (both when a game begins and each time the game is continued).

Japanese version

The Family Computer ("Famicom") version of Contra was released in Japan almost simultaneously with the American (NES) version. While the gameplay remains identical, the Famicom cartridge contains a custom-made Multi-Memory Controller that Konami produced called the VRC2 (as opposed to the UNROM chip used by the NES version), which allowed for additional graphical effects not featured in its American counterpart. The effects essentially consist of background animations, including the windblown palm leaves in Area 1, the snowstorm during parts of Area 5, and the undulating innards which comprise virtually all of Area 8. The Famicom version also features cut-scenes before each stage, including a map of the Galuga archipelago displaying the player's current location. It also features additional cheat codes (such as a stage-select code and a sound test) as well as a hidden post-credits scene which can be accessed by holding down the Select and Start buttons during the ending credits sequence.

European version

In Europe and Oceania, the NES version of Contra was retitled Probotector, and the player characters, as well as some of the enemy soldiers, were replaced with robotic counterparts. This was done to circumvent the BPjM's censorship laws in Germany, which prohibits the sales of violent video games to minors. Subsequent Contra games for the NES, Game Boy, Super NES, and Mega Drive followed suit, all being released in the PAL region under the Probotector title and featuring similar modifications. The Contra series would later retain the Contra title and characters in Europe beginning with Contra: Legacy of War.

MSX2

An MSX2 version of Contra was released by Konami exclusively in Japan on May 26, 1989. The MSX2 version of Contra greatly differs from the arcade and NES versions. Due to hardware limitations of the MSX2, the game does not scroll but instead uses flip-screens like Konami's other MSX2 games such as the original Metal Gear and Vampire Killer. The player is given a life gauge, allowing their character sustain more than one shot before losing a life. There are two main power-ups in the MSX2 version, a Falcon-shaped power-up that increases the player's walking and shooting speed, as well as a gun-shaped power-up which allows the player to change their current weapon. After picking up the weapon power-up, the player can choose between the default Normal Gun or four other weapons. The Spread Gun is not featured in this version, replaced by Rear Gun similar to the tailgun in certain Gradius games, which fires at two directions at the same time. The MSX2 Contra is composed of 19 stages. The first nine stages are based on the arcade version (which excludes the Hangar stage), while the final ten stages are new to this version. Unlike the arcade and NES versions, the MSX2 version is single-player only.

The MSX2 version of Contra was released for the Wii Virtual Console in Japan on February 2, 2010.

Later releases

A PlayStation 2 port of the arcade version of Contra was released in Japan on May 25, 2006 as part of a series of retro game ports by Hamster. A second rerelease was made for the Xbox Live Arcade on November 8 of the same year, with Digital Eclipse handling the conversion. The arcade version was also included in Konami's retro game compilation Konami Classics Series: Arcade Hits for the Nintendo DS. During Konami Mobile's tenure, several variations of Contra were released for different mobile phones, based off the arcade version.

The NES version of Contra was also included in the 2002 video game compilation Konami Collector's Series: Castlevania & Contra for Microsoft Windows in North America, which also included Super C and the three Castlevania games released for the NES. Both, Contra and Super C, are included in the Nintendo DS game Contra 4 as hidden bonuses.

Much of the game's popularity came from its two-player simultaneous gameplay, which was an uncommon feature in video games at the time of Contra's release. While successful in the arcades, the game became and remained widely popular and remembered when it was ported to the Nintendo Entertainment System in 1988. Contra was voted #1 by gaming website IGN.com as being the "Toughest Game to Beat".Nintendo Power ranked it the seventh best Nintendo Entertainment System video game, calling it one of the best multiplayer NES games.ScrewAttack named it the fifth best NES game of all time.

In 2010 IGN ranked the main antagonist Red Falcon 76th in "Top 100 Videogames Villans".

The arcade version was followed by a single sequel titled Super Contra in 1988. An NES version of Super Contra was released in the 1990, under the shortened title of Super C in North America. The NES versions of Contra and Super C were the first in a series of Contra games for home platforms. Konami would follow their releases with Operation C for the Game Boy in 1991, Contra III: The Alien Wars for the Super NES and Contra Force for the NES both in 1992, and Contra: Hard Corps for the Sega Mega Drive/Genesis in 1994. During the late 1990s, Konami externally contracted Appaloosa Interactive for the development of two sequels for the PlayStation: Contra: Legacy of War (also released for the Sega Saturn) in 1996, and C – The Contra Adventure in 1998. In the early 2000s, Konami Computer Entertainment Tokyo developed two Contra games for the PlayStation 2, Contra: Shattered Soldier in 2002 and Neo Contra in 2004. In 2007, Contra 4 was released for the Nintendo DS, a co-production between Konami of America and WayForward Technologies. Contra ReBirth, developed by M2, was released for the Wii as a WiiWare title in 2009.

The music from the arcade version of Contra is one of the soundtracks included in the video game album Konami Game Music Vol.4: A Jax, which was released by Alfa Records on May 10, 1988, in CD (catalog no. 28XA-201), cassette (ALC-22922), and vinyl (ALR-22922).

The name of the second Vampire Weekend album is a homage to this game.