Katherine J. Mack (born 1 May 1981) is a theoretical cosmologist who holds the Hawking Chair in Cosmology and Science Communication at the Perimeter Institute. Her academic research investigates dark matter, vacuum decay, and the Epoch of Reionization. Mack is also a popular science communicator who participates in social media and regularly writes for Scientific American, Slate, Sky & Telescope, Time, and Cosmos.