The GSI Helmholtz Centre for Heavy Ion Research (GSI Helmholtzzentrum für Schwerionenforschung GmbH) is a federally and state co-funded heavy ion research center in the Wixhausen suburb of Darmstadt, Germany. It was founded in 1969 as the Society for Heavy Ion Research, abbreviated GSI, to conduct research on and with heavy-ion accelerators. It is the only major user research center in the State of Hesse.

The laboratory performs basic and applied research in physics and related natural science disciplines. Main fields of study include plasma physics, atomic physics, nuclear structure and reactions research, biophysics and medical research. The lab is a member of the Helmholtz Association of German Research Centres.

Shareholdersd are the German Federal Government (90%) and the State of Hesse. Thuringia and Rhineland-Palatinate. As a member of the Helmholtz Association, the current name was given to the facility on 7 October 2008 in order to bring it sharper national and international awarenes^.

The GSI Helmholtz Centre for Heavy Ion Research has strategic partnerships with the Technical University Darmstadt, Goethe University Frankfurt, Johannes Gutenberg University Mainz and Frankfurt Institute for Advanced Studies.