She was born in Gaziantep in 1966. She completed her primary, secondary and high school education in Gaziantep and her higher education at Istanbul Technical University, Department of Chemistry and Metallurgy.

She started her career in Gaziantep Organised Industrial Zone, where she worked as a Business Engineer and Business Manager for 15 years.

In 2001, she became a founding member of the Justice and Development Party Gaziantep Province. In 2002 general parliamentary elections, she was elected as the first female deputy from Gaziantep. She served as Gaziantep deputy in the 22nd, 23rd and 24th terms in the parliament.

During her tenure at the Grand National Assembly of Turkey, she served as a member of the Industry, Trade and Energy Committee, the Turkish-EU Joint Parliamentary Committee and as the Chairman of the Investigation Committee on Violence against Women and Children.

She served as Vice President in charge of Organisation for one term and Vice President in charge of Political Affairs for another term in AK Party Headquarters Women's Branch Presidency. Between 2007-2011, she served as the President of AK Party Headquarters Women's Branch.

In the 61st government formed after the 2011 general parliamentary elections, she was appointed as the Founding Minister of the Ministry of Family and Social Policies. Thus, she became the first woman Minister of the Southeastern Anatolia Region.

In the 30 March 2014 local elections, she was elected as one of the first female metropolitan mayors in Türkiye and became the Mayor of Gaziantep Metropolitan Municipality. On 8 May 2018, she was elected as the President of the Union of Municipalities of Türkiye.

She served as the President of the Asian Mayors Forum for the period 2016-2019, Vice President of United Cities and Local Governments (UCLG) 2016 and President of United Cities and Local Governments Middle East and West Asia Chapter (UCLG MEWA).

The European Bank for Reconstruction and Development (EBRD) declared Gaziantep a "Green City" on 2 November 2021 with the initiatives of Gaziantep Metropolitan Mayor Fatma Şahin.

In 2021, she became the first mayor from Türkiye to be elected to the OECD Champion Mayors Initiative.

In 2023, she was appointed by the United Nations (UN) Secretary-General António Guterres as a member of the UN Advisory Group on Local and Regional Governments.

She served as the President of the Union of Municipalities of Türkiye between 2019-2023.

Şahin, who is married with two children, is currently serving as the Mayor of Gaziantep Metropolitan Municipality.