He was hospitalized last November after he contracted COVID-19.
Topbaş was elected mayor of Istanbul in 2004 as the candidate of the ruling Justice and Development Party (AKP) and maintained his position until 2017 when he resigned.
In 2004, he became the head of Istanbul-based United Cities and Local Governments, Middle East and West Asia Regional Government, and vice president of the United Cities and Local Governments (UCLG). He became UCLG co-chair in 2007.
Topbaş was the first politician to have won three consecutive local elections in Istanbul.
He is survived by three children and his wife.
President Recep Tayyip Erdoğan said in a tweet he was deeply saddened at the demise of Topbaş and his contributions to Istanbul and Turkey would not be forgotten.