Seydlitz was born in Kalkar in the Duchy of Cleves, where his father Daniel Florian von Seydlitz, a major of Prussian cavalry, was stationed. After his father's death in 1728 his mother brought him up in straitened circumstances, but at the age of fourteen he went as a page to the court of the Margrave Frederick William of Brandenburg-Schwedt, who had been his father's colonel. During this time under the "Mad" Margrave, Seydlitz conceived his passion for tobacco, women, and feats of daredevil horsemanship. He acquired a superb mastery of horsemanship, and many stories tell of his feats, the best known of which involved riding between the sails of a windmill in full swing.