Star Coin

Star Coins are collectibles found in New Super Mario Bros. and New Super Mario Bros Wii. Three Star Coins appear in each level where some are easy to collect, while others require special power-ups such as the Mini Mushroom or the Blue Shell to access.

In New Super Mario Bros. there are eighty levels, thus there are 240 Star Coins to find in the game. Each Star Coin adds 1,000 points to the player's game score.

They also appear in New Super Mario Bros. Wii. In this game, there are 231 Star Coins. Three Star Coins appear in each of the game's seventy-seven levels much like New Super Mario Bros. Also, it adds 4,000 points to the player's total score, instead of 1,000 like in its predecessor.

They will appear in the upcoming Nintendo 3DS game, Super Mario 3D, with a octagonal shape, yellow edge, yellow star and with the white interior, similar to Comet Medals of Super Mario Galaxy 2.

Uses

 * One use is for opening Star Gates leading to Toad Houses or bonus letter levels (e.g. 1-A or 5-B). There are thirty-two of these signs in the game, each requiring five Star Coins to open. After Mario opens the signs, he is has an option to save, allowing him to easily save his progress without completing an uncompleted tower or castle before completing the game.
 * Another use is for buying new backgrounds. After completing the game at least once, a blue Toad House will appear north of level 1-1. There are five bonus backgrounds for the Touch Screen that cost twenty Star Coins each. The fifth background that can be unlocked by opening every Toad House.
 * Once all 240 Star Coins have been collected, a second star will appear next to the save file. There will also be a message on the map screen next to the symbol, the message will display "All Star Coins spent".

Uses

 * One use is for buying Hint Movies at Peach's Castle.
 * Another use is collecting all Star Coins in a world so a level in World 9 (unlocked after beating final boss) is unlocked. It will be the level number corresponding to the world number. (e.g. collecting the Star Coins in World 1 will unlock 9-1)
 * The final use for a Star Coin is to cause a star to be displayed on the File Select Screen. If the player collects all twenty-four Star Coins in World 9, he or she will earn a star. Collecting all Star Coins in the game will also result in getting a second star.

Super Mario 3D
In the upcoming Nintendo 3DS game, Super Mario 3D, they will be three in every level, like New Super Mario Bros. games, Their uses are unknown. The Star Coins have a similar appearance to Comet Medals from Super Mario Galaxy 2, but they have stars on them instead of comets.