Joanna I of Naples (b. 1326)
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 1382; 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 as justification to avenge the death of his brother, and Joanna's 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 after, during the Western Schism, she chose to support the Avignon Papacy against Pope Urban VI, who in retaliation declared her a heretic and dethroned her on 11 May 1380.

Having all her children predecease her, Joanna's heirs were the descendants of her only surviving sister Maria, whose first marriage with their cousin Charles, Duke of Durazzo was performed without her permission, becoming both spouses in the heads of the political faction against Joanna. Trying to reconcile with the Durazzo branch and with the purpose to secure her succession, Joanna arranged the marriage of her niece Margaret of Durazzo with her first-cousin (and Joanna's second cousin) Charles of Durazzo, who eventually captured and imprisoned Joanna, and finally ordered her assassination on 27 July 1382.