Sir William Vaughan (died 1649) was an English royalist commander in the First English Civil War. He was killed at the Battle of Rathmines during the Irish Confederate Wars, fighting the English Republican army led by Michael Jones.
Almost nothing is known of Vaughan's early life, though he is often supposed to have been a member of one of the several landowning Vaughan families of Shropshire or Herefordshire. He is sometimes identified as the William Vaughan who was admitted to Shrewsbury School in 1596, which would indicate his birth date as being around 1585.
Vaughan appears to have been serving in the Irish campaign of 1643, for towards the end of the following January the Marquis of Ormonde despatched him (already described as Sir William) from Dublin at the head of some 160 horse, with which he landed early in February 1644 at Neston in Cheshire. Having joined the royalist forces at Chester under John Byron, 1st Baron Byron, he took part in Welsh and northern engagements during the ensuing summer. On 25 March, with Colonel Ellis, he defeated Thomas Mytton at Lilleshall. He defeated parliamentary cavalry at Much Wenlock on 9 May; then during May and June that year, he and his regiment took part in the campaign to relieve the besieged city of York, which ended with the disastrous Battle of Marston Moor on 2 July. In September he accompanied Byron to the relief of Montgomery. On 8 September with Sir Michael Erneley he advanced from Shrewsbury, surprised Thomas Myddelton who retreated towards Oswestry, and shut Mytton up in Montgomery. On 18 September Sir John Meldrum defeated Byron and Erneley, with Vaughan not much involved.