- Mercury (planet): The first planet from the Sun in our solar system; named after the Roman messenger of gods.
- Mercury (mythology): Roman god, counterpart to the Greek Hermes, messenger of Jupiter, the escort of dead souls to the underworld, and the patron of thieves.
- Mercury (automobile): Add brief definition or description
- Mercury (element): A chemical element, having the chemical symbol Hg, and atomic number (the number of protons) 80.
- Mercury (automobile marque): Add brief definition or description
- Project Mercury: The United States' first manned spaceflight program.