In physics, Hooke's Law of elasticity states that the extension of an elastic spring is linearly proportional to its tension.

The law holds up to a limit, called the elastic limit, or limit of elasticity, after which springs suffer plastic deformation up to the plastic limit or limit of plasticity, after which they break down.

It is named after the 17th century physicist Robert Hooke, who initially published it as an anagram ceiiinosssttuv, which he later revealed to mean ut tensio sic vis, or as the extension, the force.

Applications of the law include spring operated weighing machines. Originally the law applied only to stretched springs, but subject to physical constraints it also applies to compression springs.