George Tupou I, King of Tonga, was originally known as Tāufaʻāhau I, or Tupou Maeakafa Ngininginiofolanga in modern spelling (originally Tubou Maeakafa Giniginiofolaga). He adopted the name Siaosi (originally Jiaoji), the Tongan version of George, after King George III of the United Kingdom, when he was baptized in 1831. His nickname was Lopa-ukamea (or Lopa-ʻaione), meaning iron cable.
George Tupou was established as the Tuʻi Haʻapai (H. king) before the death of his father in 1820. He inherited the conflicts with the overlords of Tongatapu, in particular with Laufilitonga, the last Tuʻi Tonga, who tried to extend his role as spiritual leader into a more political one and contested Tāufaʻāhau in Haʻapai. The culmination of this struggle was the Battle of Velata in 1826, in which Laufilitonga was defeated.
In 1852, the last independent chief, Takai Mo Fa'e, fell and Tāufa became the undisputed leader of the whole of Tonga. His rule saw many changes in Tongan politics. He abolished serfdom in Vavaʻu in 1835, and published the Vavaʻu Code in 1838, the first written laws in Tonga. He opened the first parliament until 4 June 1862, which is still a public holiday called Emancipation Day, in Tonga.
He made Pangai Ha'apai the first capital of his realm in 1845. He then moved the capital to Nukuʻalofa in 1851 (resided in Lifuka from 1845 to 1851). On 4 November 1875 (also an holiday), the constitution was promulgated and Tonga officially became a kingdom. Siaosi then took the name George Tupou I, King of Tonga. For this reason, both 1845 and 1875 are quoted as the beginning of his reign.
He died in 1893 at the age of 96, after a swim in the sea near his palace. He was buried in the New Royal Cemetery in Malaʻekula. His children had predeceased him, so he was succeeded by his great-grandson twice over George Tupou II - the son of the daughter (ʻElisiva Fusipala Taukiʻonetuku) of his son (Tēvita ʻUnga) and the son (Siaʻosi Fatafehi Toutaitokotaha) of his daughter (Salote Pilolevu Mafileʻo).