Avşa

{{Short description|Island in Turkey}}

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File:Avsha Marmara map.jpg

Avşa Island ({{langx|tr|Avşa Adası}}) or Türkeli is a Turkish island in the southern Sea of Marmara with an area of about {{convert|20.6|km2|0|abbr=off}}.{{cite journal |last1=Kaya |first1=Hakan |title=Geomorphological features of Marmara Sea Islands |journal=International Journal of Environment and Geoinformatics |date=1 April 2019 |volume=6 |issue=1 |pages=57–66 |url=https://dergipark.org.tr/tr/download/article-file/688756 |access-date=1 February 2024 |issn=2148-9173}} It was the classical and Byzantine Aphousia ({{langx|el|Ἀφουσία}} or Ἀφησιά) and was a place of exile during the Byzantine period. The Greek inhabitants fled to Sarti Chalkidiki after the 1923 population exchange.

The island belongs to the Marmara District of Balıkesir Province in northwestern Turkey. It is a popular domestic tourist destination, especially for tourists from Istanbul. The local population is around 2,000 according to the last census, but during the summer season the number of visitors increases as far as forty to fifty thousand.