Sobhuza II (22 July 1899 – 21 August 1982) was the Chief and later King of Swaziland for 82 years, the longest verifiable reign of any monarch in recorded history.

Sobhuza was the son of Inkhosikati Lomawa Ndwandwe and King Ngwane V. His father died suddenly at the age of 23 during the yearly incwala. The incwala is the main ritual of Kingship in the Kingdom of Swaziland. This is a national event that takes place during the summer solstice. The main person in incwala is the King of Swaziland; when there is no king there is no incwala.

Sobhuza was only four months old when he was chosen to be the King with his grandmother Labotsibeni and his uncle Prince Malunge leading the Swazi nation until his maturity in 1921. Sobhuza led Swaziland through independence until his death in 1982. He was succeeded by Mswati III, his young son with Inkhosikati Ntfombi Tfwala, who was crowned in 1986.

Sobhuza II reigned Swaziland for 82 years, 254 days.

Bernhard VII reigned Lippe (HRE) for 81 years, 234 days.

William IV reigned Henneberg-Schleusingen (HRE) for 78 years, 243 days.

Heinrich XI reigned Reuss-Obergreiz (HRE) for 77 years, 103 days.

More Info: en.wikipedia.org