Liebig's Law of the Minimum, often referred to simply as Liebig's Law or the Law of the Minimum, is a law developed in agricultural science formulated by Justus von Liebig. It states that growth is controlled not by the total of resources available, but by the scarcest resource. It was originally applied to plant or crop growth. It was found that increasing the amount of plentiful nutrients did not increase growth. Only by increasing the amount of the limiting nutrient (the one most scarce in relation to "need") was growth of a plant or crop improved.

Liebig's Law has been extended to biological populations. For example, the growth of a biological population may not be limited by the total amount of resources present throughout the year, but by the minimum amount of resources available to that population at the time of the year of greatest scarcity. The growth of a population of animals might depend not on how much food was available in summer; rather on how much food was available in winter.