The Intense Pulsed Neutron Source (IPNS) is a pulsed spallation neutron source located at Argonne National Laboratory near Chicago, Illinois in the US. This facility is the outgrowth of a long line of pioneering work on pulsed spallation neutron sources begun at Argonne in the early 1970s. IPNS uses protons accelerated in the Rapid Cycling Synchrotron (RCS) to produce neutrons via the spallation process (effectively a nuclear ‘evaporation’ in which ten to fifty neutrons are released per incident proton) in a heavy-element target. These neutrons are then moderated to produce spectra peaked at thermal or subthermal energies, and directed into beams which serve a variety of instruments. Figure 1 shows a layout of the accelerator and target system, and Figure 2 shows the target/moderator system and the beamlines and instruments currently installed or under development at IPNS.