Pius "Mau" Piailug (1932 – 12 July 2010) was a Micronesian navigator from the Carolinian island of Satawal, best known as a teacher of traditional, non-instrument wayfinding methods for deep-sea voyaging. Mau's Carolinian navigation system—which relies on navigational clues using the sun and stars, winds and clouds, seas and swells, and birds and fish—was acquired through rote learning passed down through teachings in the oral tradition. He earned the title of master navigator (palu) by the age of 18, around the time the first American missionaries arrived in Satawal. As he neared middle age, Mau grew concerned that the practice of navigation in Satawal would disappear as his people became acculturated to Western values. In the hope that the navigational tradition would be preserved for future generations, Mau shared his knowledge with the Polynesian Voyaging Society (PVS). With Mau's help, PVS used experimental archaeology to recreate and test lost Hawaiian navigational techniques on the Hōkūle‘a, a modern reconstruction of a double-hulled Hawaiian voyaging canoe.
The successful, non-instrument sailing of Hōkūle‘a to Tahiti in 1976, proved the efficacy of Mau's navigational system to the world. To academia, Mau's achievement provided evidence for intentional two-way voyaging throughout Oceania, supporting a hypothesis that explained the Asiatic origin of Polynesians. The success of the Micronesian-Polynesian cultural exchange, symbolized by Hōkūle‘a, had an impact throughout the Pacific. It contributed to the emergence of the second Hawaiian cultural renaissance and to a revival of Polynesian navigation and canoe building in Hawaii, New Zealand, Rarotonga and Tahiti. It also sparked interest in traditional wayfinding on Mau's home island of Satawal. Later in life, Mau was respectfully known as a grandmaster navigator, and he was called "Papa Mau" by his friends with great reverence and affection.
He received an honorary degree from the University of Hawaii, and he was honored by the Smithsonian Institution and the Bishop Museum for his contributions to maritime history. Mau's life and work was explored in several books and documentary films, and his legacy continues to be remembered and celebrated by the indigenous peoples of Oceania.