Sir Richard Grenville, 1st Baronet (or Granville) (1600–1658) was a Cornish Royalist leader during the English Civil War.
He was the third son of Sir Bernard Grenville (1559–1636), and a grandson of the famous seaman, Sir Richard Grenville. Having served in France, Germany, and the Netherlands, Grenville gained the favour of George Villiers, 1st Duke of Buckingham, took part in the expeditions to Cádiz, to the island of Rhé and to La Rochelle, was knighted, and in 1628 became member of parliament for Fowey, Cornwall.
In 1630, he married Mary Fitz (1596–1671), the wealthy widow of Sir Charles Howard (died 1626), and was made a baronet, of Kilkhampton in the County of Cornwall; his violent temper destroyed the marriage, and he was imprisoned as the result of two lawsuits, one with his wife, and the other with her kinsman, the Earl of Suffolk. In 1633 he escaped from prison and went to Germany, returning to England six years later to join the army which Charles I was collecting to march against the Scots. Early in 1641, just after the outbreak of the Irish rebellion, Sir Richard led some troops to Ireland, where he won some fame and became governor of Trim, County Meath; then returning to England in 1643 he was arrested at Liverpool by Parliament, but was soon released and sent to join the parliamentary army.
Instead, having obtained men and money, he hurried to Charles I at Oxford and was despatched to take part in the siege of Plymouth, quickly becoming the leader of the forces engaged in this enterprise. Compelled to raise the siege he withdrew into Cornwall, where he helped to resist the advancing Parliamentarians. In 1644, parliament, for his desertion, put out a proclamation against him; in this there were attached to his name several offensive epithets, among them being skellum, a word probably derived from the German Scheim, a scoundrel. Hence he is often called "skellum Grenville."