Gebze has a population of 281,436, making it the 33rd largest place we list in Turkey. It is in Kocaeli.
Gebze holds 0.32% of Turkey's 87,926,082 people. Istanbul, the largest place we list there, is 56 times its size. The World Gazetteer published 281,436 for Gebze in 2005 and GeoNames still carries that same figure, so there is no measured change to report.
The 2005 figure comes from the World Gazetteer archive restored on this site. Why figures differ.
Nearby in size
Figures are the latest available in GeoNames (CC BY 4.0), which draws on national censuses of varying dates — treat them as recent, not same-year. Country totals are UN World Population Prospects 2024 (medium variant) where the UN lists the country separately; the handful it reports under a parent state keep a GeoNames figure and are marked as such. Sources & method.