Büyükçekmece is a district and municipality (belediye) in the suburbs of Istanbul, Turkey on the Sea of Marmara coast of the European Side, west of the city. It is largely an industrial area with a population of 380,000. The mayor is Hasan Akgün (CHP). The land around this inlet of the Sea Of Marmara, has been settled, abandoned and resettled throughout history as army after army passed along the coast to Istanbul. It is thought to be the site of the Greek colony on the Marmara shore called Athyra (Άθυρα), also known as Athyras.
The area administered by Büyükçekmece includes a large hinterland behind the Marmara shore, some of it still rural. In the centre of Büyükçekmece itself, there are still tea gardens on the seafront and other places for kids to play while their families sit, picnic and enjoy the sea views. These are now used by day trippers from the city, especially the nearby dense working-class housing areas such as Avcılar.
There are no holiday-makers now, they have moved further out from the city as since the 1950s the area has become industrialised, over-built with apartment buildings, and populated by migrants from Anatolia. Today, the inlet and the Marmara Sea are both very polluted and the infrastructure of an industrial city is now in place. Lake Büyükçekmece was connected to the sea until it was separated by a dam to supply fresh water to Istanbul. The Mimar Sinan Bridge is located in this area.