Josiah Quincy is the name of:
- Colonel Josiah Quincy I (1709–1784), Revolutionary War soldier, built Josiah Quincy House (1770)
- Josiah Quincy II (1744–1775), attorney, "the Patriot", newspaper propagandist, son of Josiah Quincy I
- Josiah Quincy III (1772–1864), president of Harvard University (1829–1845), US representative (1805–1813), mayor of Boston (1823–1828), son of Josiah Quincy II
- Josiah Quincy, Jr. (1802–1882), mayor of Boston (1846–1848), built Josiah Quincy Mansion (1848), son of Josiah Quincy III
- Josiah Phillips Quincy (1829–1910), poet, writer, publicist, son of Josiah Quincy, Jr.
- Josiah Quincy (1859–1919), General Court representative, assistant secretary of the Navy, mayor of Boston (1895–1899), son of Josiah Phillips Quincy