The ? Coin or Question Coin, is a special coin in Super Mario Galaxy. It is a large, yellow Coin with a question mark on it. When one has been collected four things can happen.
- A Mario theme will play and a line of musical notes will appear for Mario to collect. This usually causes three 1up Mushrooms to appear, or very rarely, a Power Star.
- An accumulation of Star Bits or Coins to appear.
- A Power Up will appear.
- Another ? coin will appear.
These coins appear in many galaxies like Good Egg Galaxy.