World 1 is the first world in the game Super Mario Bros., located in the Mushroom Kingdom.
 Level Information
||The first course in the game.
||The first underground course in the game.
||The first mushroom course in the game.
||The first Castle course in the game.
 Enemies Introduced
Battling the False Bowser in World 1-4
Rescuing the Mushroom Retainer in World 1-4
The Warp Zone in World 1-2
- A license plate in the Mario Kart: Double Dash!! course Mushroom City has "W 1-1" written on it. This is a reference to World 1-1. Some players have been confused that this is supposed to say 'Wii', despite that the Wii was released three years later. The same license plate has been spotted on Moonview Highway.
- Several sections of Lineland Road in Super Paper Mario are modeled after those of World 1-1. Also in Super Paper Mario, in Chapter 3-1 there's an underground section almost identical to World 1-2, but the Warp Zone leads to other parts of the area, not other worlds.
- World 1-1 and World 1-2 have been ported to the Super Smash Bros. Brawl stage, Mushroomy Kingdom. These levels have been recreated to make them look old and barren since Super Mario Bros. launched in 1985 and Brawl in 2008.
- When playing as Bowser in Paper Mario: The Thousand Year Door, Bowser will enter Worlds 1-1, 1-2, and 1-3.
- All levels in this world were released as card levels for World-e in Super Mario Advance 4: Super Mario Bros. 3. However, only World 1-1 was released outside of Japan.