William II, Duke of Brunswick-Lüneburg

William II (c. 1300–1369) of the House of Welf ruled Lüneburg from 1330 with his brother Otto III; together they expanded the estates around Gifhorn and made the Ilmenau navigable to Uelzen. After Otto died without a male heir in 1352, the succession became the problem of William's life.

He promoted his grandson Albert of Saxe-Wittenberg as heir, then changed his mind, fearing Albert's uncles' influence. In 1355 he married his younger daughter to her Brunswick cousin Ludwig, a match meant to reunite the Welf lands.

Emperor Charles IV, however, treated Lüneburg as an imperial fief falling vacant at William's death and had already enfeoffed Albert and his uncles, laying the groundwork for the Lüneburg War of Succession. Shortly before his death at Lüneburg in November 1369, William handed rule to Magnus of Brunswick.