Josiah Quincy may refer to:
- Josiah Quincy I (1710–1784), American merchant, planter, soldier, and politician
- Josiah Quincy II (1744–1775), American lawyer and patriot
- Josiah Quincy III (1772–1864), American educator and political figure, mayor of Boston, 1823–1828
- Josiah Quincy Jr. (1802–1882), American politician, mayor of Boston, 1845–1849
- Josiah Quincy (1859–1919), American politician from Massachusetts, mayor of Boston, 1896–1900
- Josiah Quincy (New Hampshire politician) (1793–1875), American politician and lawyer in New Hampshire