Co–Star is an American astrological social networking service founded in 2017,^[1] and headquartered in New York City. Users enter the date, time and place they were born to receive an astrological chart and daily horoscopes that they can compare to those of their friends.^[2]

Founder and CEO Banu Guler came up with the idea for the app after she gifted a friend's child an astrological chart that became a surprise hit at the baby shower.^[3] In 2019, Co–Star raised a $5.2 million seed round from Maveron, Aspect, and 14W, following a $750,000 pre-seed from Female Founders Fund in early 2018.^[4][5][6] In January 2020, Co–Star for Android was launched to a 120,000-person waitlist—two years after their iOS app was launched.^[6] In April 2021, Co–Star announced their $15 million Series A, led by Spark Capital.^[7] As of that date, Co–Star has more than 20 million downloads and has been downloaded by a quarter of all young women ages 18–25 in the U.S.

Co–Star employs artificial intelligence to analyze publicly accessible NASA JPL data and find patterns in a user's transits.^[8] Co–Star's algorithm maps human-written snippets of text to planetary movements to display personalized content for each user.^[5] That content has been called “slightly robotic,”^[9] “wildly beautiful,”^[5] “truly insane,"^[10] “brutally honest,”^[8] and compared to “a free therapy session.”^[11]

In July 2023, Co–Star released an in-app service called The Void that allows users to ask open-ended questions and receive answers informed by Co–Star's astrological database.^[12]

• Astrology
• NASA
• Timeline of social media