World 8-3 is the third level of World 8 in New Super Mario Bros. Wii.
The level starts out in a cavern full of lava. Throughout the level, Mario and company must contend with giant waves of lava that cause them to instantly lose a life upon contact. Hanging over the lava are chained platforms that tilt and sink when one of the characters step on them; these platforms can be found throughout most of the level's first half, with Koopa Troopas and Koopa Paratroopas placed on or around them. Shortly after the midway point is a series of tunnels that require the player to weave through incoming lava waves to pass safely. Following the tunnel is a series of weighted platforms that also sink if stepped on. Flame Chomps are found in this area. At the end is a Warp Pipe that takes players to the level's pole.
- Star Coin 1: Shortly after the beginning of the level, the first Star Coin is floating under the second chain-hanging platform. Mario and co. must stand on the left side of the platform at the right time to descend down towards the Star Coin without touching the lava.
- Star Coin 2: The second Star Coin is located in the narrow area shortly after the midway point, floating under a platform with a few other coins. Mario and co. must wait for any lava waves to pass before collecting it.
- Star Coin 3: The third Star Coin is right near the level's second Flame Chomp. Mario and co. must again wait for any lava waves to pass before jumping towards it.