The Mercury Coin is a one of the one hundred collectible Constellation Coins in Endless Ocean: Blue World. It is engraved with an image of the planet Mercury, the closest planet to the Sun in our solar system. It can be found in the Ciceros Strait area, at coordinates C-5, under a zoom-mode glow near the set of ruins known as Amphitrite's Sanctuary. This coin is one of the twelve coins needed to complete the Voice of the Night Sky quest entitled 'Solar System'.
- Mercury is the smallest planet in the Solar System.
- The planet engraved upon this coin is named after the Roman messenger of the Gods.