Prince Rupert (Prince Robert of Bavaria), a royalist general of horse during the English civil war, born in Prague, Dec. 17, 1619, died at Spring Gardens, London, Nov. 29, 1682. His mother Elizabeth was the eldest daughter of James I. of England, and the wife of Frederick V., elector palatine, who on the outbreak of the thirty years' war was elected by the insurgents king of Bohemia, and in consequence was deprived of his estates. When only 13 years old Rupert took part in the siege of Rheinberg, and at 18 commanded a regiment of cavalry in active service. At the beginning of the civil war in England he was placed at the head of a regiment of horse. He took Hereford, Lichfield, and Cirencester, and bore a prominent part in the battles of Edgehill and Chalgrove field. His daring and vigor had more than compensated for his want of prudence and military sagacity, and he was created duke of Cumberland. With Prince. Maurice he carried Bristol by assault on July 25, 1643. Afterward he scattered the parliamentary forces at Newark, and gained distinction in the north of England, especially by the relief of Latham house, held by the countess of Derby against a detachment of Fairfax's army.

The loss of the battle of Marston Moor was due to his rashness and his want of concert with the duke of Newcastle; yet he was promoted from the generalship of the horse to the command of all the forces, and took the city of Leicester. In the battle of Naseby, June 14, 1645, Prince Rupert commanded the left wing, and pursued the portion of the parliamentary army opposed to him a great distance, returning to find his own side defeated. Subsequently he took command of Bristol. The city was invested by Fairfax and Cromwell on Aug. 22, and was surrendered at the first attack (Sept. 11), the prince marching out with a convoy of two regiments of horse, and proceeding to Oxford. The same day a royal proclamation was issued revoking and annulling all military authority given to "our nephew Prince Rupert;" but in 1648 he obtained the command of that portion of the fleet which adhered to the royal cause, and with it went to the coast of Ireland to assist Lord Ormond. Anchoring in the harbor of Kinsale, he was there blockaded by Blake with the parliamentary fleet until October, 1649, when he forced his way out with the loss of a few ships.

Blake pursued him to Malaga, and in January, 1651, attacked his squadron, and destroyed all but two ships, with which the prince escaped to the West Indies. There he remained some time, supporting himself by the piratical capture of Spanish and English merchantmen, and then returned to France, selling his ships to the French government in behalf of Charles II. After the restoration he was made privy councillor. Under the duke of York he held a command in the fleet, and was present at the naval battle of Lowestoft (1655). In 1666, in conjunction with Lord Albemarle, he held command of the fleet which acted against the Dutch with various success. He was a promoter of the Hudson Bay company, and its first governor in 1670. During the latter years of his life he was governor of Windsor castle, and spent a large portion of his time in painting and engraving, and in mechanical and chemical experiments. The invention of the mezzotint has been ascribed to him, but it was made some years earlier. He improved the mechanical mode of the art, and described it in a communication to the royal society in 1662, and some of his engravings are still in existence.

He is believed to have been the inventor of pinchbeck or prince's metal, and of the glass bubbles called "Rupert's drops." (See Annealing.) He was buried in Henry VII.'s chapel, Westminster. - See Leben des Prinzen Ruprecht von der Pfalz, Anführer der Cavaliere Karl's I. von England, by Tres-kow (2d ed., Berlin, 1857), and Pfalzgraf Rupert der Cavalier, by Spruner (Munich, 1854).