Letterboxd is an online social cataloging platform designed for film enthusiasts, founded in 2011 by Matthew Buchanan and Karl von Randow in New Zealand. It allows users to log, rate, review, and share their movie-watching experiences within a vibrant community. Since its public launch in 2013, Letterboxd has grown to over 14 million users across more than 190 countries.

The platform offers various features, including film logging and journaling, where users can maintain a diary of watched films, and a rating system on a five-star scale. Users can create watchlists, engage in discussions, and access editorial content such as reviews and interviews. While the core service is free, premium memberships provide additional features like filtering films by streaming service. In 2023, Letterboxd announced plans to expand its catalog to include television shows, further enhancing its offerings for users.