María II Díaz de Haro

María Díaz I de Haro the Good (1270–1342) was a Spanish noblewoman of the House of Haro. She was the daughter of Lope Díaz III de Haro who was assassinated by order of the king at Alfaro, La Rioja. She is best known for being the Lady of Biscay and for her lifelong battle against her uncle, Diego López V de Haro for the title of the lordship of Biscay.

Maria was the daughter of Lope Díaz III de Haro and, Juana Alfonso de Molina. She inherited the title of Lord of Biscay from her brother Diego López de Haro IV upon his death in 1288, which passed briefly to her husband, John of Castile and which was later taken from her by her uncle, Diego López V de Haro during the unrest following the death of Sancho IV of Castile and the rise to power of his young son, Ferdinand IV of Castile. Her paternal grandparents were Diego López III de Haro and Constanza de Bearne.

Maria's brother was Diego López IV de Haro. She was the great granddaughter of the king, Alfonso IX of León.

Maria obtained the title of Lord of Biscay as she was next in line after her father, Lope Díaz III de Haro, died in 1288 and her elder brother, Diego López IV de Haro, died after just one year of holding the title in 1289.