Super Mario Bros. : The Lost Levels is a direct sequel to Super Mario Bros. Not to be confused with the western Super Mario Bros. 2, this sequel to Super Mario Bros. is very much an expansion to the original, with many reused graphics and concepts, though new ones are also present. The game was initially released for the Japan-only Family Computer Disk System.

One day, the peaceful kingdom where the mushroom people live was invaded by the clan of the huge turtle Bowser, who possesses powerful magic. Said magic turned the harmless mushroom people into rocks, bricks, and plants, and the Mushroom Kingdom fell into ruin. The only one who can break the magic spell and revive the mushroom people is the Mushroom Kingdom's Princess Toadstool, but she's now a prisoner of the great sorcerer king Bowser. But Mario has stood up and raised his hand, ready to defeat the members of the turtle clan, rescue Princess Peach, and once again restore peace to the Mushroom Kingdom.