Istar may refer to:
- ISTAR, a practice that links several battlefield functions together to assist a combat force in employing its sensors and managing the information they gather
- Ištar, the Assyrian and Babylonian goddess of fertility, war, love, and sex
- Istar (Dragonlance), a fictional city set in the fantasy world of Krynn in the Dragonlance setting of the Dungeons & Dragons game
- i*, a type of diagram used in requirements engineering
- Istari, the "wizards" in J. R. R. Tolkien's fictional world