Space Harrier (スペースハリアー, Supēsu Hariā) is a third-person rail shooter game, released by Sega in 1985. It was produced by Yu Suzuki, responsible for many popular Sega games. It spawned several sequels: Space Harrier 3-D (1988), Space Harrier II (1988), and the spin-off Planet Harriers (2001).

Space Harrier was originally made for the arcades, and later saw ports to many home game systems. Space Harrier's release on the Sega Master System is notable, as there were two versions: one was just like the arcade, while the other, entitled Space Harrier 3-D was actually a sequel.

It was one of the first arcade games to use 16-bit graphics and Sega's "Super Scaler" technology that allowed pseudo-3D sprite-scaling at high frame rates, with the ability to scale as many as 32,000 sprites and fill a moving landscape with them, along with over 32,000 colours displayed simultaneously on the screen. It also introduced a true analog flight stick for movement, with the ability to register movement in any direction as well as measure the degree of push, which could move the player character at different speeds depending on how far the stick is pushed in a certain direction. The game was also an early example of a third-person shooter; it was influenced by the earlier 1982 Sega game Buck Rogers: Planet of Zoom, and Space Harrier in turn influenced later 3D shooters such as Nintendo's Star Fox in 1993.

Space Harrier is set in the "Fantasy Zone", a surreal world composed of bright colors and a checkerboard-styled ground. The enemies are also unique, featuring prehistoric animals, Chinese dragons, and alien pods. The player is forced along the levels, running or flying around enemy fire, while shooting back with fireballs via the character's under-arm cannon (which doubles as a rocket-esque device allowing the character to fly). The character graphics are sprite-based, though the level backgrounds are pseudo-3D.

The arcade version of Space Harrier used digitized voices. When starting the first level, for example, the player would be greeted with "Welcome to the fantasy zone!; Get ready!". After defeating a boss, the player is assured that "You're doing great!"
Like After Burner, Space Harrier was among the first (perhaps the very first) arcade game to feature a console in which the player sits, and which moves according to the joystick movement. There is also a non-moving sit-down version and a standard upright version.
The arcade version has a total of 18 levels, each containing a boss at the end. Three exceptions are the bonus levels (5th and 12th), and the 18th level, which is a boss rush containing some of the bosses encountered up to that point.

The 3-D Battles of World Runner by Square bears a blatant resemblance to the game.