Frederick IV of Lorraine

Frederick IV, called the Fighter (1282–1328), succeeded his father Theobald II as Duke of Lorraine in 1312. Married to Elisabeth, daughter of Emperor Albert I, he backed his brother-in-law, the Habsburg claimant Frederick the Handsome, against Louis of Bavaria after the disputed election of 1314.

He fought beside Frederick at Mühldorf in 1322, where both were captured; the king of France secured his release in exchange for Lorraine's neutrality. He campaigned in Aquitaine in 1324 and in the War of Metz in 1325–1326, and was killed fighting for Philip VI at the Battle of Cassel in 1328.