- JONES-DAVIES, THOMAS ELLIS (1906 - 1960), meddyg a chwaraewr rygbi rhyng-genedlaethol
- JONES-PARRY, Madryn Llyn - gweler PARRY
- JONES-PIERCE, THOMAS - gweler PIERCE, THOMAS JONES
- JOSEFF Y SEINAD - gweler JONES, THOMAS
- JOSHUA, FRANCIS JAMES (1861 - 1920), gweinidog - gweler JOSHUA, SETH
- JOSHUA, FRANK (1861 - 1920), gweinidog - gweler JOSHUA, SETH
- JOSHUA, SETH (1858 - 1925), gweinidog (MC)
- JOYCE, GILBERT CUNNINGHAM (1866 - 1942), esgob