World's Longest-Reigning Monarch (at time of death)

King Bhumibol Adulyadej of Thailand reigned for 70 years and 126 days, from 1946 until his death in 2016, making him the longest-reigning Thai monarch and, at the time, the world's longest-reigning living monarch and head of state. He remains one of the longest-reigning sovereigns in recorded history.