A phantom loop is an electrical network that uses part of the natural environment to complete a circuit. It is a form of an open system . An example is the space tether, which uses plasma contactors and the ionosphere as parts of a circuit to extract energy from the Earth's magnetic field by electromagnetic induction. Another example is a Tesla coil, which can form a natural circuit.

Phantom loops can occur in suspended circuits, in which the conductor has no ground and uses the ionosphere to complete the circuit at both ends. Phantom loops can also occur in grounded circuit, in which the conductor has a ground and uses the lower atmosphere to complete the circuit and both ends (with the waves traversing the magnetic poles of the Earth).

See also: Electrodynamic Tethers, Tesla coil, Phantom circuit