To address the freshwater crisis in Aotearoa New Zealand, regional councils must give effect to a relatively new term, Te Mana o te Wai, which is based on a very old word: “mana”. While local understandings are emerging, questions remain among Māori about what Te Mana o te Wai means. This conceptual article reviews the literatures to discuss and define Te Mana o te Wai. Four types of mana emerge from the scholarship: mana comes from the atua; mana is a spiritual power; mana is a generative power, and mana is the authority to control. There is also a fifth aspect: mana is a power that can be taken. The answer to the question of what Te Mana o te Wai means lies in the old words.