The ATLAS Collaboration has released its first open data of heavy-ion collisions for research purposes. This dataset features lead-ion (Pb-Pb) collisions at an energy of 5 TeV per nucleon pair, recorded in 2015 as part of the Large Hadron Collider’s second operation period (LHC Run 2). Today’s release is the highest energy heavy-ion collision data ever made publicly available and the first LHC Run 2 heavy-ion open dataset.