The third biggest island depends on the criteria used to define an island. Most lists divide them by the areas. The following are some of the more common classifications used.
Islands between 500–1,000 Sq Km
Under these criteria, the third largest island would be Hiiumaa, Estonia. The total area is 989 sq km or 382 sq mi. The largest would be Maya Karimata, Indonesia. It measures 992 sq km / 383 sq mi.
Number two would be Santiago, Cape Verde. Its total area is 991 sq km / 383 sq mi. The fourth largest would be Russell Island, Canada. It has a total area of 989 sq km / 382 sq mi.
Islands between 1,000–2,500 Sq Km
The third biggest island would be Ross Island. This island is an Antarctic territory claimed by New Zealand. It measures 2,460 sq km or 950 sq mi. Navarino Island would be the largest at 2,473 sq km or 955 sq mi. This island is Chilean territory. Second would be Paramushir, Russia. Its total area is 2,471 sq km / 954 sq mi.
Fourth would be Ymer Island, Greenland, a constituent country of Denmark. It has a total area of 2,437 sq km / 941 sq mi. Fifth would be Anvers Island. It has a land area of 2,432 sq km /939 sq mi. The island is being claimed by the United Kingdom, Chile and Argentina.
Islands 2,500–5,000 Sq Km
The third largest would be Isabela, Ecuador. The island area is 4,711 sq km / 1,818 sq mi. The biggest would be Kolguyev, Russia. The land area is 4,968 sq km / 1,918 sq mi. Second would be Grande do Gurupa, Brazil. The area measures 4,864 sq km / 1,878 sq mi.
Fourth would be North Jutlandic Island (Vendsyssel-Thy), Denmark. It measures 4,685 sq km or 1,809 sq mi. Number five would be Lombok, Indonesia. Its land area is 4,625 sq km / 1,786 sq mi.
Largest Islands over 250,000 Sq Km
Borneo would be the third biggest at 748,168 sq km / 288,869 sq mi. The second largest is New Guinea. Its total area is 785,753 sq km / 303,381 sq mi. Greenland would be the largest at 2,130,800 sq km / 822,706 sq mi.
If Australia is classified as an island and not a continental landmass, it would be the largest. Greenland would be ranked at two and New Guinea will be the third biggest island.