Greece has many islands,^{[Note 1]} with estimates ranging from somewhere around 1,200^[1] to 6,000,^[2] depending on the minimum size to take into account. The number of inhabited islands is variously cited as between 166^[3] and 227.^[2]

The largest Greek island by both area and population is Crete, located at the southern edge of the Aegean Sea. The second largest island in area is Euboea or Evvia, which is separated from the mainland by the 60m-wide Euripus Strait, and is administered as part of the Central Greece region. After the third and fourth largest Greek islands, Lesbos and Rhodes, the rest of the islands are two-thirds of the area of Rhodes, or smaller.

The Greek islands are traditionally grouped into the following clusters: the Argo-Saronic Islands in the Saronic Gulf near Athens; the Cyclades, a large but dense collection occupying the central part of the Aegean Sea; the North Aegean islands, a loose grouping off the west coast of Turkey; the Dodecanese, another loose collection in the southeast between Crete and Turkey; the Sporades, a small tight group off the coast of Euboea; and the Ionian Islands, chiefly located to the west of the mainland in the Ionian Sea. Crete with its surrounding islets and Euboea are traditionally excluded from this grouping.

This article excludes the Peloponnese, which has technically been an island since the construction of the Corinth Canal in 1893, but is rarely considered to be an island due to its artificial origins.

The following are the 40 largest Greek islands listed by surface area.

Islands in the Ionian Sea are listed below. The seven largest and most popular islands are listed in bold.^[13][14]

The following islands are close to the mainland and not part of a sea:

• Geography of Greece
• Ionian Islands
• List of Aegean Islands
• Lists of islands
• List of islands of Turkey
• List of islands in the Mediterranean