William Edward Brennan (10 September 1863 – 8 October 1937) was an Australian politician.
Brennan was born and educated to elementary level in Wallsend, New South Wales.
He was an office-holder in the Colliery Employees Federation from 1903 and in 1909, after leading a strike, he was convicted of conspiracy under the Master and Servant Act and goaled at Bathurst for 3 months.
In 1925, after a number of unsuccessful attempts to win the seat of Maitland, Brennan was granted a life appointment to the New South Wales Legislative Council.
Brennan resigned this appointment to contest the seat of Hamilton at a by-election caused by the death of Hugh Connell in 1934.