Electric currents flowing through the geospace system support a highly distorted magnetic field topology, changing the Earth's dipole magnetic field into the typical magnetospheric shape. Similarly, all planetary space environments, from Venus and Mars without intrinsic dipoles, to Mercury and Ganymede with weak dipoles, to Jupiter, Saturn, Neptune, and Uranus with large dipole fields, have complex current systems related the that planet's unique magnetic topology. A number of current systems exist in magnetosphere-ionosphere systems, most notably the dayside bow shock currents, magnetopause Chapman-Ferraro currents, high latitude “region 1” field-aligned Birkeland currents, lower-latitude “region 2” field-aligned currents connected to the partial ring current, magnetotail currents, the symmetric ring current, the banana current flowing around plasma pressure peaks, Hall and Pedersen ionospheric currents, and transient currents like electrojets, interhemispheric flows, and substorm current wedges. Some of these currents are complete loops while others are segments of larger systems. These currents wax and wane in magnitude, shift in location, and sometimes disappear completely, depending on the solar activity driving the planetary environment at that time. These changes alter particle drift paths and therefore having a nonlinear feedback on the currents themselves. This session is focused on studies of current systems in geospace and other planetary environments, including characterizations of morphology and intensity, paths of loop closure, spatial and temporal dynamics, relationship with charged particle flow, and the associated magnetic field topology.