Mangaia (traditionally known as A'ua'u Enua, which means terraced) is the most southerly of the Cook Islands and the second largest, after Rarotonga.

The interior of the island is drained by underground channels passing through the makatea,[2] leading to extensive networks of caves which have been used historically as refuges and for burials.

[1] Adze heads and basalt tools show that trading contact was maintained with Rarotonga, Samoa, and Raiatea in the Society Islands.

[7][8] Initially settlement was focused on the coastal villages, but by the 16th century it had shifted inland and inter-island trade had virtually disappeared.

[10] It was visited by two more ships, one of which was possibly HMS Bounty, before the arrival of John Williams of the London Missionary Society in 1823.

[1] Williams was unable to land, but in 1824 he returned and left behind two preachers from Taha'a, who began to convert the islands to Christianity.

[1] Before the arrival of the missionaries, Mangaian society was characterised by a violent struggle between war-leaders competing for the title of mangaia (supreme temporal power), with Ariki serving as priests rather than hereditary chiefs.

[11] The last mangaia, Pangemiro, died shortly after the missionaries' arrival, and the abolition of war under Christianity effectively froze the power structure and the division of land and titles in the state they had been in 1823.

The decline of the pineapple industry and subsequent economic collapse has led to further emigration and caused the population to drop by 75% from its peak, to 499 in 2016.

[25] One anthropologist, Donald Marshall, described Mangain residents as "the most sexually active culture on record" prior to European contact, with men "[spending] their late teens and 20s having an average of 21 orgasms a week (more than 1,000 times a year).

[31] The pa tai, or coast, is dominated by coconuts, Pandanus tectorius, Barringtonia asiatica, and other scrub plants.

The Rautuitui, or upland makatea, is native forest, dominated by indigenous species such as Elaeocarpus tonganus, Hernandia moerenhoutiana, and Guettarda speciosa, with coconuts, candlenuts, and Morinda citrifolia in areas near villages and tracks.

[33] The Puna (swampy lowlands) contain the island's most fertile soils, and are dominated by introduced and cultivate species such as taro, coconut, and Hibiscus tiliaceus.

[34] The Rautuanue (slopes) and maunga (mountain) are heavily modified, and covered in pineapple, coconut, scrub, ferns, and grass.