A horseshoe orbit is the type of orbit you get when you observe an object from another nearly co-orbital one.

For example, if an object orbits the Sun in slightly less or more than a year, and if its orbit is a little more eccentric than Earth's, every year it will appear to trace a kidney-bean shape around a point on Earth's orbit. The loop is not closed but will drift forward or backward slightly each time, so that the point it circles will appear to move smoothly along Earth's orbit over a long period of time. When the object approaches Earth closely at either end of its multi-year trajectory, gravitational exchanges of energy and momentum conspire to reverse the object's apparent progress. As a result, over an entire cycle the loops will fill out a horseshoe shape, with the Earth in the horseshoe's gap.

Several asteroids (such as 3753 Cruithne and 2002 AA₂₉) are known to occupy horseshoe orbits with respect to Earth. The moons of Saturn Epimetheus and Janus occupy horseshoe orbits with respect to each other (in their case, there is no repeated looping: each one traces a full horseshoe with respect to the other).