Matawalu was a Fijian chief. He was the son of Niumataiwalu, first Roko Sau of Lau, and Uma of Nukunuku. He became the fourth Roko Sau, ruler of the Lau Islands, after the death of his brother Rasolo, but never succeeded to the title Tui Nayau. He had been similarly exiled to Nayau like Rasolo by his elder brother Uluilakeba I. When Uluilakeba I was killed by invading Bauan forces, he later lead the counter invading force for his brother Rasolo at the request of the Lakeba people. It is said that he despised the Tongans, his sister-on-law Laufitu's people and their growing influence in Lakeba. On succeeding Rasolo he removed himself to self exile on Bau Island.
His nephew, Nayacatabu, son of Uluilakeba I was left as regent in his absence, but was killed in a foray against the neighbouring island of Cicia. It was during this period that Dranivia seized power and declared himself Roko Sau. His claim to power was however short lived. While on a tour of Southern Lau, Matawalu returned to Lakeba, retook overlordship and gave orders to prevent Dranivia's return. Dranivia attempted to seize Lakeba again by force but failed.
Matawalu's dislike for Tongans resulted in direct conflict with his other nephew Roko Malani, son of Rasolo who was half Tongan through his mother Laufitu. A battle ensued between the two opposing factions and Matawalu was killed.
Matawalu married Siri of Waitabu and from him, are descended the majority of the Koroicumu noble household of the Vuanirewa clan. Matawalu has been the only recorded member of the Koroicumu noble household to have held the title Roko Sau.