Tongan Empire

The Tongan Empire was a thalassocracy that ruled the Pacific Ocean. Formally founded in 1308 AD, the Tongan Empire, mainly through the efforts of its first Tu'i Tonga Fetulikimoana, unified the entire Pacific, as well as earning land in other continents connected. At its peak, the Tongan Empire owned not just all of Polynesia, Melanesia, and Micronesia, but also northern Australia, South America, a territory of Taiwan (which was named "Hawaiki"), and had the State of Japan as a puppet.
What is believed by most to be the collapse of the Tongan Empire was in 1440 AD, when numerous monarchies owned by islands owned by Tonga seceded from the Empire, following the South African occupation, who landed in an attempt to save Tonga's stability and economy following the collapse of its ally, the Macedonian Empire years prior. Today, Tonga is now a singular monarchy, based solely on the island of Tongatapu.