L
| Name (gender) | Category | Pronunciation | Other Forms | Origin/Meaning |
|---|---|---|---|---|
| Labhraidh (m) | T | LA ra | Lowery, Labraidh | speaker |
| Labhrás (m) | T | LAV raws | Labrás | laurel bush |
| Lachtna (m) | T | LACHT na | Lucius | milk-white, milk-like |
| Lachtnán (m) | T | LACHT nawn | Lawton | dim. of Lachtna |
| Lacy | L | LAI see | deLeis | norman name, meaning is obscure |
| Laisrén (m) | T,S | LAS rain | Laisréan, Lazarus | flame |
| Laoidheach (m) | T, S | LEE ach | Laídech | songful; poetical |
| Laoire (m) | T, S | LAIR eh | Laoighaire, Leary | calf-herd |
| Laoise (f) | T | LEE sha | Leesha, Louisa | radiant girl |
| Laoiseach (m) | T | LEE shach | Lysagh, Louis, Lucius | man of Laois |
| Laragh | P | LAR a | - | place |
| Larkin | L | LAR kin | Ó Lorcáin | rough or fierce |
| Lasair (f) | T, S | LAS er | Lassar | flame; fire |
| Lasairfhiona (f) | T | la sar EE na | Lasarina, Lasairíona | flame wine |
| Lavery | L | LAV ur ee, LAIV ur ee | Ó Labhradha | speaker |
| Leannán (m) | T | LYUH nawn | - | sweetheart |
| Leary | L | LEER ee, LAIR ee | Ó Laoghaire | calf-herd |
| Lennon/Lennan | L | LEN nin | Ó Leannáin | cloak |
| Líadan (f) | T,S | LEE a din, LEE din | Liadan, Líadáin, Líadain | grey lady |
| Liam (m) | Tr | Uilliam | form of William | |
| Liamhain (f) | T | LEE uv an | - | comely |
| Life (f) | T | LIF yeh | Liffey | Celtic goddess name, gave name to river Liffey |
| Liffey | P | LIF fee | Life | Celtic goddess name- river running through Dublin |
| Líle (f) | Tr | LEE leh | Lily | form of Lily-lily flower |
| Líobhan (f) | T | LYEE von | Lí Ban | beauty of women |
| Lisburn | P | LIS burn | - | ring-fort of the gamblers |
| Lislea | P | LIS lee | Lios liadh | grey ring-fort |
| Lochlan (m) | A | LOCK lan, LOKH lan | Lochlainn, Laughlin | viking |
| Lochlann (m) | T | LOCK lan, LOKH lan | Lochlainn, Laughlin, Lochlan, Laurence | viking |
| Loinnir (f) | M | LUN neer | - | brightness, radiance |
| Lomán (m) | T,S | LUH mawn | Loman, Lommán | bare |
| Lonan (m) | A,S | LO nan | Lonán | blackbird |
| Lonán (m) | T,S | LUH nawn | Lonan | blackbird |
| Lorcan (m) | A,S | LOR can | Lorccán, Laurence | cruel or fierce |
| Lorcán (m) | T,S | LUR a cawn | Lorccán, Lorcan | cruel or fierce |
| Lowery | L | LOW ree | Ó Labhradha | speaker |
| Lucan | P,S | LOO kin | - | place of the marsh hollows |
| Lúcás | Tr | LOO kaws | Lucas, Luke | From Greek- Man from Lucania |
| Lugh (m) | T | LOO | Lug | light; brightness. A Celtic god name. |
| Lughaidh (m) | T, S | LOO ee | Lúí, Lewy, Aloysius, Louis | light; brightness |
| Luíseach (f) | T, S | LWEE shach | Luigsech, Lucy | radiant girl |