The Cook Islands are in the South Pacific Ocean, north-east of New Zealand, between French Polynesia and Fiji. There are fifteen major islands, spread over 2.2 million square kilometres of ocean, divided into two distinct groups: the Southern Cook Islands, and the Northern Cook Islands of coral atolls. The islands were formed by volcanic activity; the northern group is older and consists of six atolls (sunken volcanoes topped by coral growth). The climate is moderate to tropical.

The 15 islands and two reefs are grouped as follows:

Southern Cook Islands:
  • Nga-pu-Toru ("Three Roots", the group name for the easternmost islands of Southern Group)
  • Atiu (Enua Manu or Island of Birds)
  • Ma'uke (Akatokamanava)
  • Mitiaro (Nukuroa)
  • Remaining islands of the South:
  • Aitutaki (Araura Enua)
  • Mangaia (Auau Enua)
  • Rarotonga (Tumutevarovaro) and also with the capital, Avarua.
  • Palmerston Island (Pamati) (sometimes grouped with the Northern Group)
  • Manuae
  • Takutea
  • Winslow Reef (submerged)
  • Northern Cook Islands:
  • Manihiki (Te Fuinga O niva)
  • Nassau ( Te Nuku o Ngalewu )
  • Penrhyn Island (Tongareva or Mangarongaro)
  • Pukapuka (Te Ulu o te Watu)
  • Rakahanga (Tapuahua)
  • Suwarrow also called Suvorov
  • Tema Reef (submerged)

Administrative subdivisions
There are island councils on all of the inhabited outer islands (Outer Islands Local Government Act 1987, with amendments up to 2004 and Palmerston Island Local Government Act 1993) except Nassau, which is governed by Pukapuka (Suwarrow, with only one caretaker living on the island, also governed by Pukapuka, is not counted with the inhabited islands in this context). Each council is headed by a mayor.

The three vaka councils of main island Rarotonga established in 1997 (Rarotonga Local Government Act 1997), that were also headed by mayors, were abolished in February 2008, despite much controversy. On the lowest level, there are village committees. Nassau, which is governed by Pukapuka, has an island committee (Nassau Island Committee), which advises the Pukapuka Island Council on matters concerning its own island.