The path of least resistance describes the physical or metaphorical pathway which provides the least resistance to forward motion by a given object or entity, among a set of alternative paths. The concept is often used to describe why an object or entity takes a given path.

In physics, the path of least resistance is always taken by objects moving through a system. For example, water flowing downhill follows the path of least resistance as it is pulled downward by gravity. Electricity flowing through a circuit behaves similarly, preferentially following paths with lesser electrical resistance. Atmoshperic disturbances (storms) flow on the path of least resistance by flowing toward zones of low air pressure, where lower air density offers less impedance to the storm system than higher pressure zones.

One exception to this rule is in the realm of quantum physics, where particles behave in a probabilistic rather than deterministic manner.

The path of least resistance is also used to describe certain human behaviors, although with much less specificity than in the strict physical sense. In these cases, resistance is often used as a metaphor for personal effort or confrontation; a person taking the path of least resistance avoids these.

An important note to the concept of the path of least resistance is that it applies on a local, not global, reference. For example, water always flows downhill, regardless of whether briefly flowing uphill will help it gain a lower final altitude. In physics, this phenomenon allows the formation of potential wells, where potential energy is stored because of a barrier restricting flow to a lower energy state.