Rupert, Count Palatine of the Rhine, Duke of Bavaria (German: Ruprecht Pfalzgraf bei Rhein, Herzog von Bayern), commonly called Prince Rupert of the Rhine, (17 December 1619 – 29 November 1682), soldier, inventor and amateur artist in mezzotint, was a younger son of Frederick V, Elector Palatine and Elizabeth Stuart, and the nephew of King Charles I of England, who created him Duke of Cumberland and Earl of Holderness.

Prince Rupert had a very varied career. He was a soldier from a young age, fighting against Spain in the Netherlands (during the Eighty Years' War) and the Holy Roman Empire in Germany (during the Thirty Years' War). Aged 23, he was appointed commander of the Royalist cavalry during the English Civil War. He surrendered after the Battle of Naseby and was banished from England[2]. He spent some time in Royalist forces in exile, first on land then at sea. He then became a buccaneer in the Caribbean. Following the Restoration, Rupert returned to England, becoming a naval commander, inventor, artist, and first Governor of the Hudson's Bay Company. Prince Rupert died in England in 1682, aged 62.

Rupert was born in Prague in 1619 at the time of the Thirty Years' War. Soon after his birth, the family fled from Bohemia to the Netherlands where Rupert spent his childhood. He was almost left behind until a court member, thinking the swaddled prince was a bundle of household goods, tossed him onto a carriage. His mother, Elizabeth Stuart, sometimes known as the "Winter Queen" (due to her reign as Queen of Bohemia lasting a single winter in 1619), was a daughter of King James I of England and sister of King Charles I of England. Consequently, Rupert and his brother Maurice supported their uncle Charles when the English Civil War began in 1642.

He took to soldiering early. At the age of fourteen he fought alongside the Protestant Frederick Henry, Prince of Orange at the siege of Rheinberg in 1633, and against Spain at Breda in 1638 in the Eighty Years' War in the Netherlands.

As a child he was at times badly behaved and earned himself the nickname "Rupert The Devil". His childhood was not easy; the family had little money after leaving Prague, and he was still a teenager when his elder brother and his father died. Nevertheless Rupert was an exceptional student, becoming fluent in several European languages and excelling in art and mathematics. By the time he was 18 he stood about 6 ft 4 in tall and had become a dashing young prince.

In the Thirty Years' War, aged 19, Rupert fought for the alliance of Protestants and France at the Battle of Vlotho (17 October 1638) during the invasion of Westphalia. The forces of the Imperial General Hatzfeld captured him, imprisoning him in Linz, where he studied military textbooks. He was released on parole in 1641, on the condition that he never bear arms against the Holy Roman Emperor again.

Following the Restoration of the monarchy under Charles II, Rupert returned to the service of England, accepting an annuity and becoming a member of the privy council. He never again fought on land, but, turning admiral like Blake and Monk, he played a brilliant part in the Second Anglo-Dutch War as actual supreme commander of the British fleet from June 1666, gaining a victory in the St James's Day Battle. His efforts in the Third Anglo-Dutch War met with humiliating failure at the Battles of Schooneveld and the Battle of Texel.

At some point Rupert, a talented amateur artist, had learned of the printmaking process of mezzotint invented in 1642 by Ludwig von Siegen, a German Lieutenant-Colonel who was also an amateur artist. Whether the two ever met is a subject of scholarly controversy, but Siegen had worked as chamberlain, and probably part-tutor, to Rupert's young cousin William VI, Landgrave of Hesse-Kassel (or Hesse-Cassel), with whom Rupert discussed the technique in letters from 1654.

Rupert produced a few stylish prints in the technique, mostly copies of paintings, and introduced it to England after the Restoration. John Evelyn wrongly credited him as its inventor in 1662; apparently though Rupert invented, or perfected, the "rocker", a key tool in the process. It was Wallerant Vaillant, Rupert's artistic assistant or tutor, who first popularized the process and exploited it commercially.

In 1670, Rupert became the first Governor of the Hudson's Bay Company (HBC), after having sponsored an expedition of Radisson and des Groseilliers into Hudson Bay. Rupert's HBC secretary was Sir James Hayes (Radisson named the Hayes River, Manitoba in his honour). The HBC was granted a trading monopoly in the whole Hudson Bay watershed area, an immense territory named Rupert's Land. In 1869, control of this territory reverted to the British and Canadian governments.[3] After his retirement from the active military in around 1674, he engaged in scientific research. He is usually credited with the invention of a form of gunpowder and an alloy named "Prince's metal" in his honour. He is also credited with the invention of Prince Rupert's Drops, glass teardrops which explode when the tail is cracked. He also erected a water-mill on Hackney Marshes for a revolutionary method of boring guns, however his secret died with him, and the enterprise failed.[4]

In retirement, he continued to hold important governmental posts; from 1673, when he was 54, to 1679, he served as England's Lord High Admiral.

Prince Rupert died at his house in Spring Gardens, Westminster, on 29 November 1682, and was buried in Westminster Abbey.