Three weeks after an earthquake struck northwestern Turkey, a second earthquake struck Athens, causing Greece and Turkey to initiate "earthquake diplomacy".

An earthquake of moment magnitude 7.6 struck Kocaeli Province, Turkey on 17 August 1999. According to official figures, at least 18,373 people died and 48,901 people were injured during the earthquake, and 5,840 people were missing. At least 155 deaths were associated with the tsunami. The damage was estimated at between $12 billion and $20 billion according to various sources such as the World Bank. The earthquake was named for the epicenter's proximity to the northwestern city of İzmit. It occurred at 03:01 local time at a shallow depth of 15 km (9.3 mi). A maximum Mercalli intensity of X (Extreme) was observed. The earthquake lasted for 37 seconds, causing seismic damage, and is widely remembered as one of the deadliest natural disasters in modern Turkish history.