Sir Bevil Grenville (1596 – 5 July 1643) was a Royalist soldier in the Civil War and was killed in action at the Battle of Lansdowne in 1643. He served as MP for Cornwall 1621–1625 and 1640–1642, and for Launceston 1625–1629 and 1640.
Grenville was born near Withiel, west of Bodmin, Cornwall, the son of Sir Bernard Grenville (1567–1636) of Bideford in Devon and Stowe in the parish of Kilkhampton in Cornwall, by his wife Elizabeth Bevil, daughter and heiress of Philip Bevil and niece and heiress of Sir William Bevil. He was a grandson of Sir Richard Grenville (1542–1591), the heroic Elizabethan naval captain, explorer, and soldier. The Grenville family had for centuries been lords of the manors of Stowe in the parish of Kilkhampton in Cornwall, and of Bideford in Devon.
He was educated at Exeter College, Oxford.
Grenville was elected Member of Parliament for Cornwall in 1621 and remained so until 1625. Under King Charles I he became MP for Launceston in 1625 where he remained until King Charles I decided to rule without parliament in 1629. In parliament, Grenville supported Sir John Eliot and the opposition, and his intimacy with Eliot was lifelong. In 1639, however, he appeared as a Royalist going to the Bishop's War against Scotland in the train of King Charles. The reason for this change of allegiance is unknown, but Grenville's honour was above suspicion and he must have been convinced that he was doing right. At any rate he was a very valuable recruit to the Royalist cause, being "the most generally loved man in Cornwall." When parliament reassembled for the Short Parliament in April 1640, Grenville was chosen as MP for Launceston again. In November he was re-elected MP for Cornwall for the Long Parliament. He was disabled in 1642 for supporting the Royalists.