- JAMES, PHILIP (1664 - 1748), early Baptist minister
- JAMES, ROBERT (Jeduthyn; 1825 - 1879), musician
- JAMES, THOMAS (Llallawg; 1817 - 1879), clergyman, antiquary, and eisteddfodwr
- JAMES, THOMAS (d. 1751), early Methodist exhorter
- JAMES, THOMAS (1827 - 1899), Calvinistic Methodist minister
- JAMES, THOMAS (1834 - 1915), Calvinistic Methodist minister, and schoolmaster
- JAMES, THOMAS DAVIES (Iago Erfyl; 1862 - 1927), clergyman, and popular preacher and lecturer
- JAMES, THOMAS EVAN (Thomas ap Ieuan; 1824 - 1870), Baptist minister, and author
- JAMES, WILLIAM (1848 - 1907), Unitarian minister, schoolmaster, and public worker
- JAMES, WILLIAM (1833 - 1905), Calvinistic Methodist minister
- JAMES, WILLIAM (1836 - 1908), Calvinistic Methodist minister
- JAMES, WILLIAM (1769 - 1847), Methodist and member of the 'Trevecka Family'
- JAMES, WILLIAM (1761 - 1845), minister (Congl.)
- JAMES, Sir WILLIAM MILBOURNE (1807 - 1881), Lord Justice
- JANNER, BARNETT (BARON JANNER), (1892 - 1982), politician
- JANNER, Baron - see JANNER, BARNETT
- JARDINE, DAVID (1732 - 1766), Independent minister and head of an academy
- JARDINE, JAMES (d. 1737), Independent minister
- JARMAN, ALFRED OWEN HUGHES (1911 - 1998), Welsh scholar
- JARMAN, ELDRA MARY (1917 - 2000), harpist and author
- JARVICE, WILLIAM (d. 1743), Independent minister
- JAYNE, FRANCIS JOHN (1845 - 1921), bishop
- JE AITSH - see JONES, JOHN HERBERT
- JEDUTHYN - see JAMES, ROBERT
- JEFFREYS, GEORGE (1st baron Jeffreys of Wem), (1645 - 1689), judge
- JEFFREYS, Sir GRIFFITH Acton Hall (d. 1695) - see JEFFREYS, GEORGE
- JEFFREYS, JOHN (1718? - 1798), musician
- JEFFREYS, JOHN GWYN (1809 - 1885), conchologist
- JEFFREYS, JUSTINA (1787 - 1869), gentlewoman
- JEFFREYS, THOMAS TWYNOG (1844 - 1911), poet
- JEFFREYS, WALTER (d. 1746), banker - see WILKINS
- JEFFREYS-JONES, THOMAS IEUAN (1909 - 1967), scholar, lecturer, and warden of Coleg Harlech
- JEHU, DAVID (1812 - 1840), missionary in Sierra Leone under the Wesleyan Missionary Society
- JEHU, THOMAS JOHN (1871 - 1943), geologist
- JENKIN, JOHN (Ioan Siengcin; 1716 - 1796), poet and schoolmaster
- JENKIN, THOMAS JAMES (1885 - 1965), plant breeder and Professor of Agricultural Botany
- JENKINS, ALBERT EDWARD (1895 - 1953), rugby player
- JENKINS, DAFYDD Rhydwilym - see JENKINS, JOHN
- JENKINS, DANIEL (1856 - 1946), schoolmaster and devotee of Welsh literature and music
- JENKINS, DAVID (1912 - 2002), librarian and scholar
- JENKINS, DAVID (1582 - 1663), judge
- JENKINS, DAVID (1848 - 1915), musician
- JENKINS, DAVID Rhydwilym - see JENKINS, JOHN
- JENKINS, DAVID (fl. 1744), author - see JENKINS, HERBERT
- JENKINS, DAVID ARWYN (1911 - 2012), barrister and historian of Welsh law
- JENKINS, DAVID CYRIL (1885 - 1978), musician
- JENKINS, DAVID ERWYD (1864 - 1937), Calvinistic Methodist minister and historian
- JENKINS, DAVID LLOYD (1896 - 1966), writer, poet and schoolmaster
- JENKINS, EVAN (1781 - 1863), hymnist
- JENKINS, EVAN (1794 - 1849), cleric and schoolmaster