Sobhuza succeeded Ngwane V as Paramount Chief of Swaziland on December 10, 1899, when he was only a few months old. His grandmother, Labotsibeni Mdluli, acted as regent until December 22, 1921. His nominal reign of 82 years, 9 months is the longest precisely dated monarchical reign on record and the longest documented reign of any monarch since antiquity. Only Pepi II Neferkare of Ancient Egypt and Taejo of the ancient Korean kingdom of Goguryeo are claimed to have reigned longer.
Sobhuza's personal reign of over 60 years (1921-82) saw Swaziland's independence from Great Britain in 1968, after which he was styled King of Swaziland. When the kingdom became independent, it was hoped that the existing tribal government could be modified into a constitutional monarchy. This existed for some time, until April 12, 1973, when he repealed the constitution and dissolved parliament, making himself absolute ruler.
King Sobhuza continued the tribal practice of keeping many wives. According to the Swaziland National Trust Commission, "King Sobhuza II married 70 wives, and had 210 children between 1920 and 1970. About 180 children survived infancy, and ninety seven sons and daughters are alive as of July 2000. When he died he had over 1000 grandchildren.