Walsh is among the five most numerous surnames in Ireland, found throughout the country, with particular concentrations in Connacht in counties Mayo and Galway, in Munster in counties Cork and Waterford, and in Leinster in counties Kilkenny and Wexford. It is a semi-translation of the Irish surname Breathnach, meaning "British" or "Welsh", also sometimes anglicised as "Brannagh". The surname thus has the same historical origin as Wallace, but arrived at its present form by a more circuitous route. Unlike most of the other Hiberno-Norman families, such as the Burkes, the Fitzgeralds etc., who can trace their ancestry to a small number of known individuals, the Walshes have many different origins, since the name arose independently in many different places, for obvious reasons. Two exceptions should perhaps be mentioned: the descendants of Haylen Brenach, one of those who arrived in 1172, became very well known and prosperous in the south and east of the country, while "Walynus", who arrived in 1169, is said to have been the progenitor of the Walshes of Tirawley in Co. Mayo, and the brother of Barrett, the ancestor of the Barretts of the same county.
There are many placenames which record the surname, including at least 12 places called Walshestown.
The variant "Welsh" is particularly noted in Co. Antrim.
Thomas J. Walsh (1911-1988) was the founder and director of the Wexford Festival Opera and guided it to international recognition.
Maurice Walsh (1879-1964) began to write seriously when he was in his forties and quickly gained a large measure of fame. The film The Quiet Man is based on a short story of his, of the same name.
John Walsh (1830-1898), originally from Co. Kilkenny, became the first Catholic archbishop of Toronto.
William Walsh (1841-1921) was Roman Catholic archbishop of Dublin from 1885 to 921 and became the first Chancellor of the National University of Ireland.
Antoine Vincent Walsh (1703-1765), son of an Irish emigre to France, was Captain of the ship which landed the Young Pretender, Charles Stuart in S cotland in 1745, for which service he was knighted.
Edward Walsh (1939 - ) was the driving force behind the establishment of Limerick University in 1989 and is currently its president.