Gülsin Onay began playing the piano at the age of three and gave her first public recital on Turkish Radio at the age of six. With the assistance of a special state scholarship, she studied with Ahmed Adnan Saygun and Mithat Fenmen. Later, in Paris, her teachers included Pierre Sancan, Monique Haas, and Nadia Boulanger.

She graduated from the Paris Conservatoire at the age of 16, winning the prestigious “Premier Prix du Piano” and prizes in top international competitions such as the Marguerite Long-Jacques Thibaud (in Paris) and the Ferruccio Busoni (in Bolzano). Gülsin Onay’s international career has spanned 80 countries across all continents, from Venezuela to Japan. She has performed in major musical centers worldwide, including Amsterdam’s Concertgebouw, the Berlin Philharmonic Hall, the Vienna Konzerthaus, London’s Queen Elizabeth Hall and Wigmore Hall, the Salle Gaveau in Paris, the Washington DC National Gallery of Art, and the New York Miller Theater. She has collaborated as a soloist with leading orchestras like the Dresden Staatskapelle, Philharmonia Orchestra, English Chamber Orchestra, Royal Philharmonic, Japan Philharmonic, Munich Radio Symphony, St Petersburg Philharmonic, Tokyo Symphony, Warsaw Philharmonic, and Vienna Symphony Orchestras. Renowned conductors she has worked with include Vladimir Ashkenazy, Erich Bergel, Michael Boder, Andrey Boreyko, Jorg Faerber, Vladimir Fedoseyev, Edward Gardner, Neeme Jarvi, Emmanuel Krivine, Ingo Metzmacher, Esa-Pekka Salonen, Jose Serebrier, Vassily Sinaisky, Stanislaw Wislocki, and Lothar Zagrosek.

Gülsin Onay’s festival appearances include Berlin, Warsaw, Granada, Mozartfest Würzburg, Newport, Schleswig-Holstein, Singapore, Ohrid, Azores, and Istanbul.

Worldwide, Gülsin Onay is recognized as the definitive interpreter of the music of Ahmed Adnan Saygun, the leading Turkish composer of the 20th century. Saygun’s works prominently feature in her concerts and recordings, and his 2nd Piano Concerto, dedicated to her, was premiered in Turkey and abroad. Other contemporary composers who have dedicated works to Gülsin Onay include Hubert Stuppner, Denis Dufour, Jean-Louis Petit, Muhiddin Dürrüoğlu-Demiriz, Marc-André Hamelin, and Bujor Hoinic.

With over 20 recorded albums, Gülsin Onay showcases the breadth of her repertoire and interpretive power, ranging from solo works and concertos from Haydn and Mozart to the contemporary era. Her 2007 CD featuring live concert recordings of Tchaikovsky’s 1st and Rachmaninov’s 3rd Piano Concerto received acclaim. In 2008, CPO released her recording of both Saygun concertos to widespread critical acclaim. To commemorate Beethoven’s 250th anniversary, Gülsin Onay recorded 2 CDs of the composer’s works. Her latest release, featuring piano concertos by Ulvi Cemal Erkin and Khachaturian, received wide critical praise. Many of her concerts have been broadcast on European radio and television and, in the USA, on National Public Radio.

During the 2020–2021 coronavirus pandemic, Gülsin Onay became a regular performer on social media, where her livestreamed concerts garnered several million views.

Gülsin Onay holds the title of State Artist in her native Turkey, where she has been the official soloist for the Presidential Symphony Orchestra in Ankara for many years. She is “Artist in Residence” at Bilkent University in Ankara and holds honorary doctoral degrees from Bosphorus University in Istanbul and Hacettepe University in Ankara. In 2007, she received the State Medal from the Polish nation for her interpretation of Chopin’s music. The same year, the “Sevda-Cenap And” Music Foundation awarded her its prestigious 2007 Honorary Award Gold Medal. Gülsin Onay was named “Pianist of the Year” in the 2011 Donizetti Classical Music Awards. In 2014, she received the Honorary Medal of the 42nd Istanbul Music Festival, and in 2018, the Honorary Medal from the Bodrum Music Festival. Since 2015, the Turkish city of Tekirdağ, which named one of its streets after Gülsin Onay, has organized an annual concert series “Gülsin Onay Piano Days” in her honor.

Beyond her professional performing career, Gülsin Onay has been a tireless promoter of classical music through her charitable activities, event organization, teaching, and broadcasting. Since 2003, she has been a “Goodwill Ambassador” for UNICEF and regularly gives charity concerts to support and publicize their activities. She has been the Artistic Advisor of the International Gümüşlük Classical Music Festival and Academy since its foundation in 2004. Gülsin Onay takes a particularly keen interest in nurturing the development of young musicians and has taught over 400 pupils. She is a regular contributor to radio and television arts programs and, since 2017, has hosted her own weekly program “In the Studio with Gülsin Onay” on Turkish national radio.