WELF or GUELPH, a princely family of Germany, descended from Count Warin of Altorf (8th century), whose son Isenbrand is said to have named his family Welfen, i.e. whelps. From his son Welf I. (d. 824) were descended the kings of Upper Burgundy and the elder German line of Welf. Welf III. (d. 1055) obtained the duchy of Carinthia and the March of Verona. With him the elder line became extinct, but his grandson in the female line, Welf IV. (as duke, Welf I.), founded the younger line, and became duke of Bavaria in 1070. Henry the Black (d. 1126), by his marriage with a daughter of Magnus, duke of Saxony, obtained half of the latter’s hereditary possessions, including Lüneburg, and his son Henry the Proud (q.v.) inherited by marriage the emperor Lothair’s lands in Brunswick, &c., and received the duchy of Saxony. The power which the family thus acquired, and the consequent rivalry with the house of Hohenstaufen, occasioned the strife of Guelphs and Ghibellines (q.v.) in Italy. Henry the Lion lost the duchies of Bavaria and Saxony by his rebellion in 1180, and Welf VI. (d. 1191) left his hereditary lands in Swabia and his Italian possessions to the emperor Henry VI. Thus, although one of the Welfs reigned as the emperor Otto IV., there remained to the family nothing but the lands inherited from the emperor Lothair, which were made into the duchy of Brunswick in 1235. Of the many branches of the house of Brunswick that of Wolfenbüttel became extinct in 1884, and that of Lüneburg received the electoral dignity of Hanover in 1692, and founded the Hanoverian dynasty of Great Britain and Ireland in 1714. For its further history see Hanover. The Hanoverian legitimists in the German Reichstag are known as Welfen.
See Sir A. Halliday, History of the House of Guelph (1821); R. D. Lloyd, Origin of the Guelphs; F. Schmidt, Die Anfänge des welfischen Geschlechts (Hanover, 1900).