- REES, JOHN THOMAS (1857 - 1949), musician
- REES, JONATHAN (Nathan Wyn; 1841 - 1905), poet, essayist, and eisteddfodwr
- REES, JOSIAH (1744 - 1804), Unitarian minister
- REES, LEIGHTON THOMAS (1940 - 2003), world champion darts player
- REES, LEWIS (1710 - 1800), Independent minister
- REES, MERLYN (1920 - 2006), politician
- REES, MORGAN GORONWY (1909 - 1979), writer and university administrator
- REES, OWEN (1717 - 1768), Independent minister
- REES, OWEN (1770 - 1837) - see REES, JOSIAH
- REES, REES ARTHUR (Rhys Dyfed; 1837 - 1866), poet
- REES, RICE (1804 - 1839), cleric and scholar
- REES, RICHARD (1707 - 1749), Arminian Independent minister
- REES, RICHARD JENKIN (1868 - 1963), minister (Presb.)
- REES, ROBERT (Eos Morlais; 1841 - 1892), vocalist and musician
- REES, ROBERT OLIVER (1819 - 1881), apothecary, publisher, and author
- REES, SARAH JANE (Cranogwen; 1839 - 1916), schoolmistress, poet, editor, temperance advocate
- REES, SUSANNAH WESLEY (1863 - 1933) - see REES, BOWEN
- REES, THOMAS (1815 - 1885), Independent minister, and historian
- REES, THOMAS (1869 - 1926), principal of Bala-Bangor Independent College
- REES, THOMAS (Twm Carnábwth; 1806? - 1876), pugilist
- REES, THOMAS (1862 - 1951), breeder of Welsh cobs
- REES, THOMAS (1777 - 1864), Unitarian minister - see REES, JOSIAH
- REES, THOMAS (1825 - 1908), minister (CM)
- REES, THOMAS IFOR (1890 - 1977), HM Ambassador
- REES, THOMAS JAMES (1875 - 1957), director of education
- REES, THOMAS MARDY (1871 - 1953), Independent minister, historian and author
- REES, THOMAS WYNFORD (Dagger; 1898 - 1959), major-general
- REES, TIMOTHY (1874 - 1939), bishop of Llandaff
- REES, WALTER ENOCH (1863 - 1949), contractor and long-standing secretary of the Welsh Rugby Union
- REES, WILLIAM (1808 - 1873), printer and publisher
- REES, WILLIAM (Gwilym Hiraethog; 1802 - 1883), Independent minister, writer editor, and political leader
- REES, WILLIAM HOPKYN (1859 - 1924), missionary, linguist, author
- REES, WILLIAM JENKINS (1772 - 1855), cleric and antiquary
- REES, WILLIAM THOMAS (Alaw Ddu; 1838 - 1904), musician
- REES-DAVIES, IEUAN (1894 - 1967), musician and author
- REES-WILLIAMS, DAVID REES - see WILLIAMS, DAVID REES
- REICHEL, Sir HENRY RUDOLF (1856 - 1931), principal of University College, Bangor
- REICHEL, Sir HENRY RUDOLF - see REICHEL, Sir HARRY
- RELLY family
- RELLY, JAMES (1722 - 1778), Universalist preacher - see RELLY
- RELLY, JOHN (d. 1777), Universalist preacher - see RELLY
- RENDEL, 1st Baron - see RENDEL, STUART
- RENDEL, STUART (1st baron Rendel), (1834 - 1913), industrialist, Member of Parliament, and philanthropist
- REUBEN BRYDYDD Y COED - see DAVIES, REUBEN
- REUBEN, BERNICE RUTH (1923 - 2004), novelist
- REYNOLDS, JOHN (fl. 1739), antiquary
- REYNOLDS, JOHN (1759 - 1824), Baptist minister
- REYNOLDS, JONATHAN OWAIN (Nathan Dyfed; 1814 - 1891), author
- REYNOLDS, LLYWARCH OWAIN (1843 - 1916), Celtic scholar - see REYNOLDS, JONATHAN OWAIN
- RHIRID FLAIDD (fl. 1160), nobleman and warrior