The concept of the struggle for existence (or struggle for life) concerns the competition or battle for resources needed to live. It can refer to human society, or to organisms in nature. The concept is ancient, and the term struggle for existence was in use by the end of the 18th century. From the 17th century onwards the concept was associated with a population exceeding resources, an issue shown starkly in Thomas Robert Malthus’ An Essay on the Principle of Population which drew on Benjamin Franklin's Observations Concerning the Increase of Mankind, Peopling of Countries, etc..

It is sometimes forgotten that Charles Darwin used the term "struggle for existence" in what he called a metaphorical sense. This was because he used it to refer not only to direct competition between (and within) species but indirect competition (as with a plant at the edge of the desert). Darwin noted that the struggle for existence could also involve active or passive mutual aid between organisms of the same or different species, instancing social insects (see also symbiosis).

Darwin made the term the title of his third chapter in On the Origin of Species published in 1859. Taking up Malthus's idea of the struggle for existence, Darwin was able to develop his view of adaptation, which was highly influential in the formulation of the theory of natural selection. In addition, Alfred Wallace independently used the concept of the struggle for existence to help come to the same theory of evolution. Later, T.H. Huxley further developed the idea of the struggle for existence. Huxley did not fully agree with Darwin on natural selection, but he did agree that there was a struggle for existence in nature. Huxley also recognized that a struggle for existence existed between competing ideas within the minds of people engaged in intellectual discussion. This view is an early example of what was later described as meme theory.

While the idea of the struggle for existence was developing in the western world, there were other interpretations of the struggle for existence, especially by Peter Kropotkin in Russia. Borrowing the phrase mutual aid from Darwin, he published Mutual Aid: A Factor of Evolution , partially as a response to an essay called "The Struggle for Existence" by Huxley. Also, the struggle for existence was questioned in the United States in the 1930s, as the idea of cooperation among organisms became popular. More recently, it has been argued that the struggle for existence is not as important on macroevolutionary time scales.