John Francis "Jack" Shelley (September 3, 1905 – September 1, 1974) was a U.S. politician. He served as the 35th mayor of San Francisco, from 1964 to 1968, the first Democrat elected to the office in 50 years, and the first in an unbroken line of Democratic mayors that lasts to the present (as of 2020). His term in the United States House of Representatives, immediately prior to his mayoralty (1949-1964), also broke a long streak of Republican tenure (44 years) and began a streak of Democratic representatives for San Francisco (and, coincidentally, the 5th district) that continues to the present (as of 2018).