Béatrix de Cusance, Baroness of Belvoir (27 December 1614 – 5 June 1663), was the second wife of Charles IV, former reigning Duke of Lorraine.

To avoid a scandal, her mother arranged a marriage to Leopold-Eugène Perrenot de Granvelle, Prince of Cantecroix (1615–1637), maternal grandson of Rudolf II, Holy Roman Emperor through his extramarital daughter Caroline, Margravine of Austria (1591-1662), whom she married in 1635.

[1] His marriage to Béatrix de Cusance was not deemed valid by the Roman Catholic church, which had not authorised his divorce from Nicole.

The couple separated in April 1642 following his excommunication, which was the consequence of his second marriage; earlier, in 1639, Béatrix gave birth to a girl named Anne, whom Charles recognized.

Béatrix lived in Brussels, where she hosted a salon and arranged concerts as one of the city's leading social figures.