The High Luminosity Large Hadron Collider (HL-LHC; formerly referred to as HiLumi LHC) is an upgrade to the Large Hadron Collider, operated by the European Organization for Nuclear Research (CERN), located at the French-Swiss border near Geneva. From 2011 to 2020, the project was led by Lucio Rossi. In 2020 the lead role was taken up by Oliver Brüning.

The upgrade started as a design study in 2010, for which a European Framework Program 7 grant was allocated in 2011, with goal of boosting the accelerator's potential for new discoveries in physics. The design study was approved by the CERN Council in 2016 and HL-LHC became a full-fledged CERN project. The upgrade work is currently in progress and physics experiments are expected to start taking data at the earliest in 2028.

The HL-LHC project will deliver proton-proton collisions at 14 T e V {\displaystyle \mathrm {TeV} } with an integrated luminosity of 3000 f b − 1 {\displaystyle \mathrm {fb^{-1}} } for both ATLAS and CMS experiments, 50 f b − 1 {\displaystyle \mathrm {fb^{-1}} } for LHCb, and 5 f b − 1 {\displaystyle \mathrm {fb^{-1}} } for ALICE. In the heavy-ion sector, the integrated luminosities of 13 n b − 1 {\displaystyle \mathrm {nb^{-1}} } and 50 n b − 1 {\displaystyle \mathrm {nb^{-1}} } will be delivered for lead-lead and proton-lead collisions, respectively. The inverse femtobarn (reference