King Tupou I was the first king of the Kingdom of Tonga, reigning from 1845 until his death in 1893. He is known for unifying the islands of Tonga and establishing a constitutional monarchy, which helped to modernize the nation. His leadership played a crucial role in maintaining Tongan sovereignty during a time of colonial expansion in the Pacific. Under King Tupou I's rule, significant reforms were implemented, including the introduction of a written constitution in 1875. This constitution laid the foundation for the political system in Tonga and ensured the rights of its citizens. His legacy continues to influence Tongan society and governance today.