Wilhelmina (born July 3, 1709, Berlin, Prussia [Germany]—died Oct. 14, 1758, Bayreuth, Upper Franconia) was the sister of Frederick the Great of Prussia and margravine of Bayreuth (from 1735).
She shared the unhappy childhood of her brother, whose friend and confidante she remained most of her life. She married Frederick, hereditary prince of Bayreuth, in 1731; when he became margrave in 1735, the pair set about making Bayreuth a miniature Versailles. They rebuilt the Bayreuth palace and the Bayreuth opera house, as well as other structures, and founded the University of Erlangen. The Margravine made Bayreuth one of the intellectual centres of Germany, surrounding herself with a little court of wits and artists which gained added prestige from the occasional visits of Voltaire and Frederick the Great. With the outbreak of the Seven Years’ War, Wilhelmina’s interests shifted from dilettantism to diplomacy. She acted as eyes and ears for her brother in southern Germany until her death.