Sir William Augustus Fraser, 4th Baronet (10 February 1826 – 17 August 1898), of Pilton House, near Barnstaple, Devon, was an English politician, author and collector.

He was elected member of parliament for Barnstaple (Devon) in 1852, and again in 1857, and for Ludlow (Shropshire) in 1863 and for Kidderminster (Worcestershire) in 1874.

He was the eldest son and heir of Sir James Fraser, 3rd Baronet, a colonel of the 7th Hussars, who had served on Wellington's staff at the Battle of Waterloo in 1815.

He was returned for Barnstaple in 1852, but the election was declared void on account of bribery, and the constituency was disfranchised for two years.

He was a familiar figure at the Carlton Club, always ready with a copious collection of anecdotes of Wellington, Benjamin Disraeli and Napoleon III.