Kaʻahumanu ("The Feathered Mantle", March 17, 1768 – June 5, 1832) was queen consort and acted as regent of the Hawaiian Kingdom as Kuhina Nui. She was the favorite wife of King Kamehameha I and also the most politically powerful, and continued to wield considerable power as co-ruler in the kingdom during the reigns of his first two successors.

Kaʻahumanu was born in a cave called Puu Kauiki in Hāna on the Hawaiian island of Maui. She was born on March 17, 1768. The present Kaʻahumanu Society celebrates her birthday on March 17.

Kaʻahumanu's father was Keʻeaumoku Pāpaʻiahiahi, a fugitive aliʻi (noble) from the island of Hawaiʻi, and her mother was Nāmāhānaikaleleokalani, daughter of Mō'ī Kekaulike Kalaninui Kui Hono and wife of her half-brother, the late king of Maui, Kamehamehanui. Through her mother, she was related to many aliʻi nui of Maui. Through her father, she was the third cousin of Kamehameha I, both sharing the common ancestor, Princess Kalanikauleleiaiwi of the island of Hawaiʻi. She was named after her father's rival, Kahekilinuiʻahumanu, because it was from him that her father was fleeing at the time.

Her siblings include Governor John Adams Kuakini of the island Hawaiʻi, Queen Kalākua Kaheiheimālie, and Governor George Keʻeaumoku II of Maui.^{[citation needed]}

Her father became an advisor and friend to Kamehameha I, eventually serving as the royal governor of Maui. He arranged for Kaʻahumanu to marry him when she was thirteen years old. Kamehameha had numerous wives, but Kaʻahumanu would become a favourite and encouraged his war to unify the islands.

Kaʻahumanu was one of Kamehameha I's favorite wives and his most powerful. Upon Kamehameha's death on May 8, 1819, Kaʻahumanu announced that late king had wished that she share governance over the Kingdom of Hawaiʻi with his 22-year-old son Liholiho, who took the name of Kamehameha II. The council of advisors agreed and created the post of kuhina nui for her, which was similar to co-regent or modern-day prime minister. Her power base grew and she ruled as Queen Regent during the reigns of both Kamehameha II and Kauikeaouli, who assumed the throne as Kamehameha III.

In some ways Kaʻahumanu was ahead of her time and championed the rights of native Hawaiian women, although this was to her own advantage. In what became known as the 'Ai Noa (free eating), Kaʻahumanu conspired with Keōpūolani, another of her late husband's wives who was also Kamehameha II's mother, to eat at the same table with the young king. Notably, she also convinced the Kahuna-nui (translatable to High Priest) of the kingdom, Hewahewa, to support her efforts to abolish the kapu. While breaking a major kapu was a death penalty offence, Kamehameha II refused to kill his mother, Keōpūolani; this event effectively broke the monarchy's support of the kapu, and resulted in the system being outlawed.

The island of Kauaʻi and its subject island Niʻihau had never been forcibly conquered by Kamehameha. After years of resistance they negotiated a bloodless surrender in the face of Kamehameha's armada. In 1810 the island's King, Kaumualiʻi, became a vassal to Kamehameha. When Kamehameha I died, Kamehameha II and Kaʻahumanu feared Kauaʻi would break away from the kingdom. To preserve the union they kidnapped Kaumualiʻi on October 9, 1821, and Kaʻahumanu married him by force. After Kaumualiʻi died in 1824, and a rebellion by Kaumualiʻi's son Humehume was put down, she married his other son Kealiʻiahonui.