He was the son of John Bagwell, M.P., and Mary, née Hare. He was the Member of Parliament for Rathcormack in the Parliament of Ireland from 1798 until the Union with Great Britain at the end of 1800, when the constituency of Rathcormack was disenfranchised.
He was elected at a by-election in 1801 as MP for constituency of Clonmel in the Parliament of the United Kingdom and held that seat until his resignation in 1819 to fight a by-election for the Tipperary seat when the prior member succeeded to the Irish Peerage as Earl of Glengall. He won the seat and held it until the 1826 general election
He resided at the family mansion at Marlfield, Clonmel.
- Hansard 1803–2005: contributions in Parliament by William Bagwell
|Parliament of the United Kingdom|
|Vacant|| Member of Parliament for Clonmel
Montague James Mathew and
Richard Butler, Viscount Caher
| Member of Parliament for Tipperary
March 1819 – 1826
With: Richard Butler, Viscount Caher, to April 1819
Francis Aldborough Prittie, from April 1819
Francis Aldborough Prittie and