The Anti-Mask League of San Francisco was an organization formed to protest an ordinance which required people in San Francisco, California to wear masks during the 1918 influenza pandemic. The ordinance it protested lasted less than one month before being repealed. Due to the short period of the league's existence, its exact membership is difficult to determine; however, an estimated 4,000–5,000 citizens showed up to a meeting to protest the second ordinance in January 1919.[1] Opposition to similar ordinances during the COVID-19 pandemic in the United States led to renewed interest in, and comparisons with, the Anti-Mask League.