when was the first papal conclave

The first official papal conclave, as established by the rules of Pope Gregory X in 1274, was held in January 1276 in Arezzo, Tuscany. This conclave followed the constitution "Ubi periculum," which formalized the practice of locking cardinals in seclusion during the election to prevent outside political or personal interference. The first pope elected in this conclave was Innocent V. Before this formal establishment, papal elections had occurred but not under the strict conclave rules. The term "conclave" itself comes from the Latin "cum clave," meaning "with a key," signifying the practice of locking the cardinals away. Thus, the first papal conclave in the legal and formal sense dates to January 1276.