Byrne, Ralph Henry (1877–1946), architect, was born 25 April 1877 in Dublin, third among five sons and one daughter of William Henry Byrne (1844–1917), architect, and May Anna Gertrude Byrne (née Dillon). W. H. Byrne worked in partnership with John O'Neill of Belfast from about 1869; they opened a Dublin branch in 1874 and Byrne practised on his own after O'Neill's death in 1883. His practice extended throughout Ireland and is particularly associated with catholic church architecture. Ralph was educated at St George's School, Weybridge, Surrey, was articled to his father (1896–1901), and became his partner in the firm (1902), renamed William H. Byrne & Son. They worked closely together, designing the church of St Agatha, North William St., Dublin (completed 1909) in Roman renaissance style, with an aisleless nave creating a spacious interior. After his father went blind in 1913, Ralph took over the practice and designed the Hibernian Bank building (1917–19) (later used by the Irish Permanent Building Society) in Sackville (O'Connell) St., its ornate facades and steeply pitched roof reminiscent of the French renaissance style.
Ralph's varied and extensive practice included rebuilding, in dignified Georgian style, the National Maternity Hospital, Holles St., Dublin (completed 1937), possibly Europe's first fully electrified hospital; SS Peter and Paul, Athlone, Co. Westmeath (foundation stone laid 1932); the church of the Sacred Heart, Cardonagh, Co. Donegal (1941–5); and the two classical-style cathedrals of Christ the King, Mullingar, Co. Westmeath (foundation stone 1933, dedicated 1936), and SS Patrick and Felim, Cavan (cornerstone 1939, dedicated 1942) – a Romanesque basilica with a Corinthian portico and a tower rising 190 ft (58 m).
His wife's nephew Simon Aloysius Leonard (1903–76) became his partner (1936). He was a member (1902), fellow (1920), and vice-president (1938) of the RIAI, and member (1906–46) of the AAI. His commitment to high standards in his work and to his clients, and his easy and approachable manner earned him both the affection and respect of his colleagues and friends. He died 15 April 1946 at his home, 9 Ailesbury Rd, Dublin, and was buried in Glasnevin cemetery. He married (1905) Mary Josephine Mangan of Dunboyne Castle; they had one son, who died in 1940.