Liquid argon detectors are ubiquitous in particle, astroparticle, and applied physics. They reached an unprecedented level of maturity thanks to more than 20 years of research and development and the operation of large-scale facilities at CERN, Fermilab, and the Gran Sasso laboratories. This review discusses such an impressive advance, from the grounding of the experimental technique up to cutting-edge applications. The review commences by describing the physical and chemical properties of liquid argon as an active and target medium for particle detection, together with advantages and limitations compared with other liquefied noble gases. The opportunities and challenges of liquid argon detectors operated as calorimeters, scintillators, and time projection chambers are examined. The core applications of liquid argon detectors at colliders (ATLAS), accelerator neutrino beams (SBN and DUNE), and underground laboratories (DarkSide, DEAP, and ICARUS) for the observation of rare events are then delved into. The review concludes by looking at unconventional developments (pixelization, combined light-charge readout, Xe-doped devices, and all-optical readout) and applications in medical and applied physics to extend this technology’s scope toward novel research fields.

• Cosmic ray & astroparticle detectors
• Dark matter detectors
• Neutrino detection
• Particle detectors