Sir William Osborne, 8th Baronet PC (died November 1783), was an Irish baronet and politician.
Osborne was the son of Sir John Osborne, 7th Baronet and Editha Proby, and succeeded in the baronetcy in 1743. He served as High Sheriff of County Waterford in 1750 and was a Member of Parliament in the Irish House of Commons for Carysfort between 1761 and 1768 and for Dungarvan between 1768 and 1783 and again in 1783, and was sworn of the Irish Privy Council in 1770.
Osborne married Elizabeth, daughter of Thomas Christmas, of Whitfield, County Waterford, in 1749. They had several children, including John Proby Osborne, Sir Thomas Osborne, 9th Baronet, Sir Henry Osborne, 11th Baronet and Charles Osborne. Osborne died in November 1783 and was succeeded by his son, Thomas.