An image forming apparatus includes a cartridge including a portion-to-be-positioned, and an apparatus main body on which the cartridge is mounted in a mounting direction. The apparatus main body includes a positioning portion and a regulating portion. The positioning portion positions the cartridge by engaging with the portion-to-be-positioned. The regulating portion is provided on an upstream side of the positioning portion in the mounting direction. The cartridge includes a portion-to-be-regulated provided on an upstream side of the portion-to-be-positioned in the mounting direction. The portion-to-be-positioned engages with the regulating portion before engaging with the positioning portion, to regulate movement of the cartridge in the direction orthogonal to the mounting direction. The portion-to-be-regulated engages with the regulating portion before the portion-to-be-positioned engages with the positioning portion, to regulate movement of the cartridge in the direction orthogonal to the mounting direction.