Rally-X (Japanese: ラリーX, Hepburn: Rarī-Ekkusu) is a 1980 maze chase video game developed and published by Namco for arcades in Japan and Germany; it was distributed in North America by Midway Manufacturing and in Europe by Karateco. Players drive a blue Formula One race car through a multidirectional scrolling maze to collect yellow flags. Boulders block some paths and must be avoided. Red enemy cars pursue the player in an attempt to collide with them. Red cars can be temporarily stunned by laying down smoke screens at the cost of fuel. Rally-X is one of the first games with bonus stages and continuously playing background music.

Rally-X was designed as a successor to Sega's Head On (1979), an earlier maze chase game with cars. It was a commercial success in Japan, where it was the sixth highest-grossing game of 1980, but Midway released the game in North America to largely underwhelming results. The game is known in North America for an often-repeated, though untrue, story involving its demonstration at the 1980 Amusement & Music Operators Association trade show, where the attending press believed Rally-X was of superior quality than the other games presented, specifically Pac-Man. Though it was well-received by attendees, Rally-X failed to attract much attention during its presentation.

Reception for Rally-X, both at release and retrospectively, has highlighted its technological accomplishments and high difficulty. Some reviewers have found it to be influential and ahead of its time. Rally-X received several remakes and sequels, beginning with the slightly tweaked New Rally-X in 1981. It is also included in several Namco compilations.

Rally-X is a maze chase game where the player controls a blue Formula One racecar. The objective is to collect yellow flags that are scattered around an enclosed maze while avoiding collision with red-colored cars that pursue the player. Mazes scroll in the four cardinal directions and are clustered with dead ends, long corridors, and stationary boulders that are harmful to the player. Each level contains ten flags that increase their point value when collected in succession. One of the flags is a "Special Flag", indicated by an S next to it, which doubles the value of each flag collected thereafter. The player can temporarily stun the red cars with smoke screens, which depletes a portion of their fuel meter at the right of the screen. The meter constantly depletes the longer the player takes in a level, and acts as a timer. As the game progresses, more red cars are added and become more aggressive.

The player has a radar beneath their fuel meter, which displays their current position on the map as well as the location of the flags and red cars. The third level and every fourth thereafter is a bonus round (called a "Charanging Stage"), where the objective is to collect the flags in a certain amount of time. In these bonus rounds, the red cars remain idle and will not chase the player unless their fuel is empty.

Rally-X was created by Namco and designed by Hirohito Ito, with hardware developed by Kouichi Tashiro. It was produced as a successor to Head On (1979), an older arcade game from Sega that similarly involved collecting items in a maze while avoiding enemy cars that pursued the player. Head On was a popular title in Japanese arcades, which gave Namco the idea of creating a game that built on its mechanics. Rally-X was created on a version of the Pac-Man arcade system board that supports multi-directional scrolling. The programming was done by Kazuo Kurosu, who went on to design the multi-directional shooter Bosconian (1981), and featured music from Pac-Man composer Toshio Kai.

Rally-X was first demonstrated in Japan in January 1980, before receiving a wide release on October 3, 1980. When preparing to release the game overseas, Namco believed Rally-X had more foreign appeal than Pac-Man with its audiovisual presentation and challenge, which it believed American audiences would prefer to the simplicity and "cuteness" present in Pac-Man. Namco presented Rally-X at the 1980 Amusement & Music Operators Union (AMOA) tradeshow in Chicago, Illinois, alongside Pac-Man, King & Balloon, and Tank Battalion. An often-repeated story is that out of the games presented, specifically Pac-Man, the attending industry analysts believed Rally-X was the stand-out and the one destined to be successful. Though it received praise from the press, Rally-X did not attract much attention during the event. According to Play Meter magazine, both Pac-Man and Rally-X received mild attention at the show. Midway Manufacturing, the video game division of Bally Manufacturing, agreed to distribute Rally-X and Pac-Man in North America. Dave Marofske, the president of Midway, believed the two had the most potential out of the four Namco games presented. Midway released Rally-X in North America in February 1981 in upright, tabletop, and cabaret cabinet variations.

A home conversion of Rally-X was released for the VIC-20 in Japan in 1981. The port was developed by HAL Laboratory and published by the Japanese division of Commodore International. Due to licensing restrictions, HAL changed the game's characters to mice and cats and released it in North America as Radar Rat Race. Namco released a port for the MSX in 1984 that adopted the gameplay of New Rally-X, which was released in Europe by Argus Press Software under the Bug-Byte name. Dempa Shinbun developed versions for the Fujitsu FM-7, MZ-1500, and Sharp X1 computers in Japan the same year.