ATLAS is a general-purpose particle physics experiment at the Large Hadron Collider (LHC) at CERN. It is designed to exploit the full discovery potential of the LHC, pushing the frontiers of scientific knowledge. ATLAS’ exploration uses precision measurement to push the frontiers of knowledge by seeking answers to fundamental questions such as: What are the basic building blocks of matter? What are the fundamental forces of nature? What is dark matter made of? ATLAS is the largest detector ever constructed for a particle collider: 46 metres long and 25 metres in diameter. Its construction pushed the limits of existing technology. ATLAS is designed to record the high-energy particle collisions of the LHC, which take place at a rate of over a billion interactions per second in the centre of the detector. More than 100 million sensitive electronics channels are used to record the particles produced by the collisions, which are then analysed by ATLAS scientists. ATLAS is a collaboration of physicists, engineers, technicians, students and support staff from around the world. It is one of the largest collaborative efforts ever attempted in science, with over 5,500 members and almost 3,000 scientific authors. The success of ATLAS relies on the close collaboration of research teams located at CERN, and at member universities and laboratories worldwide.