Oceania is a geographical region that includes Australasia, Melanesia, Micronesia, and Polynesia. Spanning the Eastern and Western hemispheres, Oceania is estimated to have a land area of 8,525,989 square kilometres and a population of around 44.5 million as of 2021. When compared with the other continents, the region of Oceania is the smallest in land area and the second smallest in population after Antarctica. Its major population centres are Sydney, Melbourne, Brisbane, Perth, Auckland, Adelaide and Honolulu.