Gemini (Gem-en-i.e.) is the third astrological sign in the Zodiac, originating from the constellation of Gemini. In astrology, Gemini is considered a "masculine", positive (extrovert) sign. Perhaps the most dominant Geminian characteristic is versatility. It is also considered an air sign, and is one of four mutable signs. Gemini has been closely associated with the planet Mercury and is considered to be ruled by it. Being the third sign of the zodiac, Gemini has been associated with the astrological third house.

Individuals born when the Sun was in this sign are considered Gemini individuals. Under the tropical (western) zodiac, Sun is in the sign of Gemini roughly from May 20 to June 21, ending at the moment of summer solstice by definition. In western astrology, this sign is no longer aligned with the constellation as a result of the precession of the equinoxes.[citation needed] Under the sidereal zodiac, it is currently there roughly from June 15 to July 15. The Sanskrit name of Gemini in Hindu astrology is Mithuna.