- MATTHEWS, NORMAN GREGORY (1904 - 1964), chancellor
- MAURICE family Clenennau, Glyn (Cywarch), Penmorfa
- MAURICE, DAVID (1626 - 1702), cleric and translator
- MAURICE, HENRY (1634 - 1682), Independent minister
- MAURICE, HENRY (1647 - 1691), cleric and author
- MAURICE, HUGH (1775 - 1825), skinner, and transcriber of Welsh manuscripts
- MAURICE, JANE (1812), hymnist - see MAURICE, HUGH
- MAURICE, MATHIAS (1684 - 1738), Independent minister and writer
- MAURICE, PETER (1803 - 1878), cleric - see MAURICE, HUGH
- MAURICE, ROWLAND JONES, translator of Nennius - see MAURICE, HUGH
- MAURICE, WILLIAM (d. 1680), antiquary and collector of manuscripts
- MAURICE, Sir WILLIAM (1542 - 1622), politician
- McBRIDE, NEIL (1910 - 1974), Labour politician
- McGRATH, MICHAEL JOSEPH (1882 - 1961), Archbishop
- McLUCAS, CLIFFORD (1945 - 2002), artist and theatre director
- MEADOWS, JOSEPH KENNY (1790 - 1874), draughtsman
- MECHELL Saint - see MALO, Saint
- MEILYR ap GWALCHMAI, poet - see GWALCHMAI ap MEILYR
- MEILYR BRYDYDD (fl. c . 1100-1137), chief court-poet
- MEIRIADOG - see EDWARDS, JOHN
- MELISSA - see BRERETON, JANE
- MENAI - see EVANS, ALFRED THOMAS
- MENANDER - see MORGAN, CHARLES LANGBRIDGE
- MENDS, CHRISTOPHER (1724? - 1799), Methodist exhorter, afterwards Independent minister
- MEPHIBOSETH - see JONES, JOHN
- MERCER, JACK - see MERCER, JOHN
- MERCER, JOHN (1893 - 1987), cricketer
- MERCH MYRDDIN - see HUGHES, ELIZABETH PHILLIPS
- MERÊD - see EVANS, MEREDYDD
- MEREDITH, BENJAMIN (1700 - 1749), Baptist minister
- MEREDITH, BILLY - see MEREDITH, WILLIAM
- MEREDITH, Sir JOHN (1714 - 1780), lawyer
- MEREDITH, JOHN ELLIS (1904 - 1981), minister (Presbyterian Church of Wales) and author
- MEREDITH, LEWIS (Lewys Glyn Dyfi; 1826 - 1891), preacher and writer
- MEREDITH, RICHARD (d. 1597), bishop of Leighlin, Ireland
- MEREDITH, RICHARD (1826 - 1856), author - see MEREDITH, LEWIS
- MEREDITH, ROBERT (1823 - 1893), printer of Welsh books and music in the U.S.A.
- MEREDITH, THOMAS (fl. 1747-1770), Methodist exhorter, and Antinomian
- MEREDITH, WILLIAM (1874 - 1958), footballer
- MEREDUDD ap RHYS (fl. 1450-1485), gentleman, cleric, and poet
- MEREDYDD LLWYD Glynllifon (fl. c. 1413-1456) - see GLYN
- MERFYN FRYCH (d. 844), king of Gwynedd
- MERRETT, Sir HERBERT HENRY (1886 - 1959), industrialist
- MERRICK, Hascard, Fleet, Bush, Wigmore - see MEYRICK
- MERRICK, RHYS - see MEURUG, RHYS
- MERRICK, RICE (d. 1586-7), landed gentleman, genealogist, and historian
- MERRICK, RICE - see MEURUG, RHYS
- MERTHYR of SENGHENYDD, 1st Baron - see LEWIS, WILLIAM THOMAS
- MERTHYR TYDFIL, 1st Baron EVANS of - see EVANS, HORACE
- MEUDWY MÔN - see JONES, OWEN