- Not to be confused with the Princes' Islands, which are also a group of islands in the Sea of Marmara, a few miles off the Asian coast of Istanbul.
The Marmara Islands (Turkish: Marmara Adaları) are an archipelago in the Sea of Marmara (Turkey), located in its mid-west portion, near its exit to Aegean Sea (the Straits of Dardanelles) and off Kapıdağ Peninsula on the Asian coast.
- Marmara Island — the major island of the group, mostly mountainous with windswept hills to north and pine forests to south
- Avşa — the most popular (and accordingly crowded) island with sandy beaches and vineyards
- Paşalimani — a low-lying rural island with several villages along its amoeba-like coastline
- Ekinlik — the smallest island, inhabited by locals with a conservative worldview
The four main islands that constitute the archipelago are Marmara Island, Avşa, Paşalimani, and Ekinlik. There are also a few other, uninhabited or seasonally inhabited islets and rocks surrounding and inbetween these islands, but for the most part, they remain inaccessible.
While the Marmara Islands are all administerively part of the Balıkesir Province, they are grouped into two separate districts of that province. The northwestern trio of Marmara, Avşa, and Ekinlik make up the Marmara District, and Paşalimanı forms a part of the Erdek District, which encompasses the mainland Kapıdağ Peninsula as well.
Turkish is the native language spoken in the islands.
Year-round boats which can accommodate cars from Tekirdağ (on the northern/European coast of the Sea of Marmara; costs 15 TL/person) and Erdek (on the southern/Asian coast of the Sea of Marmara). There are also pessenger-only fast ferries  from Istanbul during summer months, which cost 40 TL/person (or 30 TL/person with a slower ferry departing on Saturdays).
Most ferries which connect mainland to the islands call at almost all inhabited islands, so they can also be used for hopping island to island, although Paşalimanı and Ekinlik is served less frequently than Marmara and Avşa, at which practically all ferries call. You’ll have no problems on inter-island transportation once you get to the harbour of any given island.
All of the islands had significant local Greek populations up to the 1920s, so some architectural heritage, such as historical houses or monasteries can be seen on the islands, if sometimes partially ruined.
The telephone code for the islands is 266 (+90 266 when calling from out of Turkey).