| William Salusbury-Trelawny | |
| Office: | Member of Parliament for Cornwall East |
| Term Start: | 1832 |
| Term End: | 1837 |
| Alongside: | Sir William Molesworth |
| Predecessor: | New constituency |
| Successor: | Edward Eliot Sir Hussey Vivian |
| Birth Name: | William Trelawny |
| Birth Date: | 4 July 1781 |
Sir William Lewis Salusbury-Trelawny, 8th Baronet (4 July 1781 – 15 November 1856), was a British politician.
Born William Trelawny, he assumed in 1802 the additional surname of Salusbury.
He served as High Sheriff of Cornwall in 1811[1] and later sat as member of parliament for Cornwall East from 1832 to 1837. He served as Lord-Lieutenant of Cornwall from 1839 to 1856.
Salusbury-Trelawny died in November 1856, aged 69. He had married in 1807 Patience Christian Carpenter; they had several children. He was succeeded by his second son John as his eldest son Owen had died at a young age in 1830.