Charles IV (5 April 1604 – 18 September 1675) was Duke of Lorraine from 1624 until his death in 1675, with a brief interruption in 1634, when he abdicated under French pressure in favor of his younger brother, Nicholas Francis.

Gaston d'Orléans, frequently sided with either branch of the Habsburg family against Richelieu, who was de facto ruler of France as its Chief Minister, and had to flee several times to avoid charges and trial for treason.

On one visit to the ducal court at Nancy, the widowed Gaston fell in love with Charles's 15-year-old sister and married her secretly, which so infuriated the king that he convened the clergy of France and the Parlement of Paris to void the marriage, giving consent only on his death bed.

In that circumstance and sense, Charles was a casualty of the fierce factional infighting in the French court between the King's brother Gaston d'Orléans, and Cardinal Richelieu, even though technically, Lorraine was subject to the Holy Roman Empire and the Emperor Ferdinand II of Austria.

Forced to make humiliating concessions to France, he abdicated under the French pressure and invasion in 1634 in favor of his brother, Nicholas Francis, and entered the imperial service in the Thirty Years' War and was victorious at the Battle of Nördlingen.

Appointed captain general of the troops in Burgundy, Charles defended the core area of the Franche-Comté around Besançon, Dole and Salins against the French over the next few years.

Bernard, however, used the advantage of the inner line and was able to repulse Charles at Thann on 15 October as well as Johann von Götzen's attack on the siege positions around Breisach a few days later.

Traditional accounts of the Cromwellian wars often dismiss the appeal to Lorraine as an act of desperation, but recently one historian has argued that the stateless Duke was in fact seriously interested in becoming the Protector of Ireland.