Justine Ezarik is an American YouTube personality, host, and actress. She is best known as iJustine, with over a billion views across her YouTube channels since 2006. She gained attention as a lifecaster who communicated directly with her millions of viewers on her Justin.tv channel, ijustine.tv.

In May 2014, Simon & Schuster announced that its Atria Publishing Group division had partnered with United Talent Agency to publish books by a group of social media stars that included iJustine. Her book – titled I, Justine (ISBN 1476791511) – was released on June 2, 2015. Fast Company writer David Zax described the book, "Ezarik wound up writing a sort of work of investigative journalism about herself by digging into a morass of tweets, photos, and videos to help remind herself who she is."