The LHCf ("Large Hadron Collider forward") is a special-purpose Large Hadron Collider experiment for astroparticle (cosmic ray) physics, and one of seven detectors in the LHC accelerator at CERN. The other six are: ATLAS, ALICE, CMS, MoEDAL, TOTEM, and LHCb. LHCf is designed to study the particles generated in the "forward" region of collisions, those almost directly in line with the colliding proton beams. It therefore consists of two detectors, 140 m on either side of the interaction point. Because of this large distance, it can co-exist with a more conventional detector surrounding the interaction point, and shares the interaction point IP1 with the much larger general-purpose ATLAS experiment.