The Habsburg Netherlands was a personal union of fiefs owned by the Holy Roman Empire that existed in the Low Countries from 1482 to 1581. The personal union began in 1482 when the Duchy of Burgundy's possessions in the Low Countries were inherited by the son of Duchess Mary of Burgundy and Emperor Maximilian I of Germany, Philip I of Castile, who belonged to his father's House of Habsburg. Philip died in 1506, the same year as his accession to the throne of Castile, and his son Charles, the future King of Spain and Holy Roman Emperor, inherited the lands. Under a 1522 inheritance treaty signed with his brother Ferdinand I of Germany, Charles divided the Habsburg empire between Spain and the Empire, and he gave the Netherlands to Spain as the "Spanish Netherlands", while a few regions (such as Guelders) remained Imperial fiefs. As a result of the Protestant Reformation, religious tensions would lead to the north seceding as the Union of Arras in 1581, leading to the Dutch Revolt and the separation of the Habsburg Netherlands into the southern Spanish Netherlands and the northern, Dutch-ruled United Provinces.