Joanna I of Naples

Joanna I, also known as Johanna I (Italian: Giovanna I; December 1325 – 27 July 1382), was Queen of Naples, and Countess of Provence and Forcalquier from 1343 to 1381; she was also Princess of Achaea from 1373 to 1381.

Joanna was the eldest daughter of Charles, Duke of Calabria and Marie of Valois to survive infancy. Her father was the son of Robert the Wise, King of Naples, but he died before his father in 1328. Three years later, King Robert appointed Joanna as his heir and ordered his vassals to swear fealty to her. To strengthen Joanna's position, he concluded an agreement with his nephew, King Charles I of Hungary, about the marriage of Charles's younger son, Andrew, and Joanna. Charles I also wanted to secure his uncle's inheritance to Andrew, but King Robert named Joanna as his sole heir on his deathbed in 1343. He also appointed a regency council to govern his realms until Joanna's 21st birthday, but the regents could not actually take control of state administration after the King's death.

Joanna's personal life crucially affected the political stability of the Kingdom of Naples (murder of her first husband Andrew in 1345, the invasions of King Louis I of Hungary—justified as avenging the death of his brother—and her three later marriages with Louis of Taranto, James IV, titular King of Majorca and Otto, Duke of Brunswick-Grubenhagen) and undermined her position with the Holy See; moreover afterwards, during the Western Schism, she chose to support the Avignon Papacy against Pope Urban VI, who in retaliation declared her a heretic and usurper on 11 May 1380.