William Flower, 1st Baron Castle Durrow

William Flower, 1st Baron Castle Durrow PC (Ire) (11 March 1685 – 29 April 1746) was an Anglo-Irish peer and politician.

Political career He sat as Member of Parliament (MP) for County Kilkenny from 1715 to 1727. when he was raised to the peerage as "Baron Castle Durrow, of Castle Durrow in the County of Kilkenny".

He owned a substantial property at Abercynrig in Brecon. He inherited it from his stepmother, the Welsh heiress Dorothea Jeffreys. She was the only daughter of Colonel John Jeffreys, first Master of the Royal Hospital Kilmainham, and widow of Arthur Turner (died 1684), judge of the Court of Common Pleas (Ireland). He built Castle Durrow, Durrow, County Laois, as his principal Irish residence: the family remained there until 1922.

Jonathan Swift praised him as "a gentleman of very good sense and wit".

Family He was the only son of Thomas Flower of Finglas and his first wife Mary Temple, daughter of Sir John Temple, Speaker of the Irish House of Commons, and Jane Yarner. His paternal grandparents were Sir William Flower, MP and Privy Councillor, and Frances Weldon. They had two daughters and two sons. His daughter Rebecca, married James Agar, a prominent County Kilkenny politician, and was the mother of six children, including George Agar, 1st Baron Callan.

Flower died in 1746 aged 61 and was buried at Finglas in County Dublin. His only surviving son Henry succeeded to the barony. and became the first Viscount Ashbrook in 1751.