Super Mario Bros.: The Lost Levels is a 1986 platform game developed and published by Nintendo as the sequel to Super Mario Bros. (1985). The games are similar in style and gameplay, with players controlling Mario or Luigi to rescue Princess Peach from Bowser. The Lost Levels adds a greater level of difficulty and Luigi controls slightly differently from Mario, with reduced ground friction and increased jump height. The Lost Levels also introduces obstacles such as poison mushroom power-ups, counterproductive level warps, and mid-air wind gusts. The game has 32 levels across eight worlds and 20 bonus levels.

Super Mario Bros.: The Lost Levels was originally released in Japan for the Famicom Disk System as Super Mario Bros. 2[a] on June 3, 1986, following the success of its predecessor. It was developed by Nintendo R&D4 – the team led by Mario creator Shigeru Miyamoto – and designed for players who had mastered the original. Nintendo of America deemed it too difficult for its North American audience and instead chose another game as the region's Super Mario Bros. 2: a retrofitted version of the Japanese Doki Doki Panic.