An island is a piece of landmass smaller than a continent and surrounded entirely by water. Although most islands are formed naturally, others like Flevopolder and René-Levasseur Island are artificial islands, constructed by people. Islands occur in rivers and lakes, although the largest islands are found in oceans or seas. Although continental landmasses are surrounded entirely by water, they are not islands because of their massive sizes. However, some geographers refer to Australia (the smallest continent) as an island despite it being almost four times larger than Greenland.

　　It is difficult to figure out the number of islands on planet Earth because not all islands have been discovered. The world oceans have not been fully explored and chances are there could be more islands than the current estimated figure. However, there are thousands of islands in the oceans with varying sizes, shapes, flora, fauna, climate, and geography. Most islands are either tropical or volcanic islands, with Sumatra (Indonesia) as the world’s largest volcanic island

　　Although the world's oceans and other water bodies are dotted with thousands of islands, most of these islands are have smaller surface areas. Only about 322 islands have surface areas greater than 1,000 square kilometers. Of these larger islands, about 179 have areas of at least 2,500 square kilometers, while the next 30 largest islands cover between 2,000 and 2,499 square kilometers. Five Islands, Baffin, Madagascar, Borneo, New Guinea, and Greenland, are at least 500,000 square kilometers.

　　Greenland is the world’s largest and only island whose area exceeds one million square kilometers. Its size, 2.13 million square kilometers, is almost one-fourth the size of Australia, the world’s smallest continent. However, New Guinea (the second-largest island) is the world’s highest island, at 5,030 meters, and home to Oceania’s highest peak. Indonesia, which possesses the western half of New Guinea (second-largest island), Sumatra, Sulawesi, and Java, is the world’s largest island country. Here are the world’s largest islands and some of the largest lake islands.

　　

The 10 Largest Islands In The World

Rank	Island	Area (sq. km)	Area (sq mi)
1	Greenland	2,175,600	840,004
2	New Guinea	785,753	303,381
3	Borneo	748,168	288,869
4	Madagascar	587,713	226,917
5	Baffin	503,944	194,574
6	Sumatra	443,066	171,069
7	Honshu	225,800	88,982
8	Great Britain	209,331	80,823
9	Victoria	220,548	85,154
10	Ellesmere	183,965	71,029

　　NOTE: Australia is widely considered as a continental landmass, not an island. It certainly is the largest island, with a size of (2,966,153 sq miles) (7,682,300 sq km).

　　

10 Largest Island Countries

Rank	Country	Area (sq. km)	Area (sq mi)
1	Indonesia	1,904,569	735,358
2	Madagascar	587,041	226,658
3	Papua New Guinea	462,840	178,704
4	Japan	377,915	145,913
5	Malaysia	329,847	127,355
6	Philippines	300,000	115,831
7	New Zealand	268,838	103,798
8	United Kingdom	243,610	94,058
9	Cuba	110,860	42,804
10	Iceland	103,000	39,769

　　Read More10 Largest Islands Countries In The World

　　

10 Highest Islands In The World

Rank	Island	Height (feet)	Height (meters)
1	New Guinea	16,503	5,030
2	Hawaii, US	13,796	4,205
3	Borneo, Indonesia	13,698	4,175
4	Formosa, China	13,114	3,997
5	Sumatra, Indonesia	12,484	3,805
6	Ross, Antarctica	12,448	3,794
7	Honshu, Japan	12,388	3,776
8	South Island, NZ	12,349	3,764
9	Lombok, Indonesia	12,224	3,726
10	Tenerife, Spain	12,188	3715

　　Read MoreHighest Islands In The World

　　

10 Largest Lake Islands In The World

Rank	Island, Lake	Country	Area (sq. km)	Area (sq mi)
1	Manitoulin, Lake Huron	Canada	2,766	1,068
2	Rene-Lavasseur, Manicouagan Reservoir	Canada	2,020	780
3	Olkhon, Lake Baikal	Russia	730	282
4	Samosir, Lake Toba	Indonesia	630	243
5	Isle Royal, Lake Superior	United States	535.4	209
6	Ukerewe, Lake Victoria	Tanzania	530	205
7	St. Joseph, Lake Huron	Canada	365	141
8	Drummond, Lake Huron	United States	347	134
9	Idjwi, Lake Kivu	DR Congo	340	110
10	Ometepe Island, Lake Nicaragua	Nicaragua	276	107

　　Read More10 Largest Lake Islands In The World

　　

10 Largest Islands In The USA

Rank	Island	State	Area (sq. km)	Area (sq mi)
1	Hawaii	Hawaii	10,434	4,029
2	Kodiak	Alaska	9,510	3,672
3	Puerto Rico	NA	8,710	3,588
4	Prince of Wales	Alaska	6,675	2,577
5	Chichagof	Alaska	5,388	2,080
6	Saint Lawrence	Alaska	4,430	1,710
7	Admiralty	Alaska	4,362	1,684
8	Nunivak	Alaska	4,227	1,632
9	Baranof	Alaska	4,064.5	1569
10	Unimak	Alaska	4,119	1,590

　　

10 Largest Islands In Europe

Rank	Island	Area (sq. km)	Area (sq mi)	Countries/regions
1	Great Britain	229,848	88,745	United Kingdom ( England, Scotland, Wales)
2	Iceland	101,826	39,315	Iceland
3	Ireland	84,421	32,595	Ireland, United Kingdom (Northern Ireland)
4	Severny Island	47,079	18,177	Russia
5	Spitsbergen	37,673	14,546	Norway (Svalbard)
6	Yuzhny Island	33,246	12,836	Russia
7	Sicily	25,662	9,908	Italy
8	Sardinia	23,949	9,247	Italy
9	Nordaustlandet	14,443	5,576	Norway (Svalbard)
10	Cyprus	9,251	3,572	Cyprus Northern Cyprus United Kingdom (Akrotiri and Dhekelia)

　　Read MoreThe Largest Islands Of Europe By Area