Prince Wilhelm of Urach, Count of Württemberg, 2nd Duke of Urach, was a German prince who was elected in June 1918 as King of Lithuania, with the regnal name of Mindaugas II. He never assumed the crown, however, as German authorities declared the election invalid; the invitation was withdrawn in November 1918. From 17 July 1869 until his death, he was the head of the morganatic Urach branch of the House of Württemberg.

Morganatic marriage, sometimes called a left-handed marriage, is a marriage between people of unequal social rank, which in the context of royalty or other inherited title prevents the principal's position or privileges being passed to the spouse, or any children born of the marriage. The concept is most prevalent in German-speaking territories and countries most influenced by the customs of the German-speaking realms.