- LEWIS, TIMOTHY (1877 - 1958), Welsh and Celtic scholar
- LEWIS, TIMOTHY RICHARDS (1841 - 1886), surgeon, pathologist, and pioneer in tropical medicine
- LEWIS, TITUS (1773 - 1811), Baptist minister
- LEWIS, TITUS (1822 - 1887), antiquary
- LEWIS, Sir WILFRID HUBERT POYER (1881 - 1950), judge
- LEWIS, WILLIAM (fl. 1786-1794), hymn-writer
- LEWIS, WILLIAM (1814 - 1891), Calvinistic Methodist missionary and linguist
- LEWIS, WILLIAM (1835? - 1918), printer and publisher
- LEWIS, WILLIAM BEVAN (1847 - 1929), alienist
- LEWIS, WILLIAM HOWELL (1793? - 1868), minister (Congl.)
- LEWIS, WILLIAM JAMES (1847 - 1926), mineralogist
- LEWIS, WILLIAM MORRIS (1839 - 1917), minister (Presb.)
- LEWIS, WILLIAM MORTIMER (1840 - 1880), Baptist college principal
- LEWIS, Sir WILLIAM THOMAS (first BARON MERTHYR of SENGHENYDD), (1837 - 1914), coal magnate
- LEWIS, WYNDHAM (1780 - 1838), M.P.
- LEWSYN YR HELIWR - see LEWIS, LEWIS
- LEWYS ap HYWEL (fl. c. 1560-1600), poet
- LEWYS ap RHYS ab OWAIN - see DWNN, LEWYS
- LEWYS GLYN COTHI - see LEWIS GLYN COTHI
- LEWYS GLYN DYFI - see MEREDITH, LEWIS
- LLYWELYN ap RHISIART (fl. 1520-1565), Chief Bard of the Three Provinces', and one of the most notable poets in the history of Glamorgan
- LEWYS SHANCO LEWIS - see LEWIS, LEWIS
- LEWYS, DAFYDD (d. 1727), cleric
- LHUYD, EDWARD (1660 - 1709), botanist, geologist, antiquary, and philologist
- LHUYD, HUMPHREY - see LLWYD, HUMPHREY
- LHWYD, EDWARD - see LHUYD, EDWARD
- LINDEN, DIEDERICH WESSEL (d. 1769), medical doctor and mineralogist
- LIVSEY, GEORGE FREDERICK (1834 - 1923), bandmaster
- LLAETHFERCH - see EVANS, MARY JANE
- LLALLAWG - see JAMES, THOMAS
- LLANERCHYDD - see PARRY, THOMAS
- LLANOVER, Lady - see HALL, AUGUSTA
- LLANOVER, Lord - see HALL, BENJAMIN
- LLAWDDEN - see HOWELL, DAVID
- LLAWDDEN (fl. 1450), cywyddwr
- LLAWDDOG (fl. 600?), saint
- LLEF O'R NANT - see JONES, JOHN
- LLEISION ap MORGAN ap CARADOG ap IESTYN - see MORGAN ap CARADOG ap IESTYN
- LLEISION ap THOMAS (fl. 1513-1541), last abbot of Neath
- LLEUDDAD Saint - see LLAWDDOG, Saint
- LLEURWG - see MORGAN, JOHN RHYS
- LLEW LLWYFO - see LEWIS, LEWIS WILLIAM
- LLEW MADOG - see MORGAN, EVAN
- LLEW TEGID - see JONES, LEWIS DAVIES
- LLEWELLIN, MARTIN - see LLUELYN, MARTIN
- LLEWELLYN, Sir DAVID RICHARD (1879 - 1940), coalowner
- LLEWELLYN, DAVID TREHARNE (1916 - 1992), Conservative politician
- LLEWELLYN, THOMAS (1720? - 1783), Baptist minister and tutor
- LLEWELLYN, THOMAS REDVERS (1901 - 1976), singer and teacher of singing
- LLEWELYN ALAW - see LLEWELYN, THOMAS DAVID