An example game controller is removably attachable to a main unit. The game controller includes a controller-side slide member. The controller-side slide member protrudes from a first surface of the game controller and is configured to slidably engage with the main unit-side slide member in a slide direction. The controller-side slide member has a first end and a second end in the slide direction, and the game controller is configured to be attached to the main unit by inserting the controller-side slide member into the main unit-side slide member. The controller-side slide member includes a protruding portion and at least one terminal. The protruding portion protrudes from the first end side of the controller-side slide member in the slide direction and has a facing surface that faces the first surface of the game controller. The at least one terminal is between the facing surface and the first surface.