How many ghosts are in the original Pac-Man? There are four: Blinky, Pinky, Inky, and Clyde.
These four ghosts are the original Ghost Gang in Namco's 1980 arcade game. Each has a distinct color, name, and movement strategy, giving the maze more variety than a simple chase. Blinky is red, Pinky is pink, Inky is cyan, and Clyde is orange.
The ghosts do not all behave identically. Blinky directly pursues Pac-Man, Pinky tries to ambush him by targeting the space ahead of him, Inky uses a more complicated targeting method, and Clyde alternates between chasing and retreating depending on his distance from Pac-Man. Their different personalities were designed to keep the game challenging without making every encounter predictable.
This answer refers specifically to the original arcade Pac-Man. Later games, spin-offs, television adaptations, and expanded versions introduced additional ghosts, which can cause confusion. Ms. Pac-Man, for example, added Sue to the familiar group, but Sue was not one of the four ghosts in the original Pac-Man arcade game.