Thomas Robert Malthus (; 13/14 February 1766 – 29 December 1834) was an English economist, cleric, and scholar influential in the fields of political economy and demography.

In his 1798 book An Essay on the Principle of Population, Malthus observed that an increase in a nation's food production improved the well-being of the population, but the improvement was temporary because it led to population growth, which in turn restored the original per capita production level. In other words, humans had a propensity to utilize abundance for population growth rather than for maintaining a high standard of living, a view that has become known as the "Malthusian trap" or the "Malthusian spectre". Populations had a tendency to grow until the lower class suffered hardship, want and greater susceptibility to war famine and disease, a pessimistic view that is sometimes referred to as a Malthusian catastrophe. Malthus wrote in opposition to the popular view in 18th-century Europe that saw society as improving and in principle as perfectible.

Malthus saw population growth as inevitable whenever conditions improved, thereby precluding real progress towards a utopian society: "The power of population is indefinitely greater than the power in the earth to produce subsistence for man." As an Anglican cleric, he saw this situation as divinely imposed to teach virtuous behavior. Malthus wrote that "the increase of population is necessarily limited by subsistence," "population does invariably increase when the means of subsistence increase," and "the superior power of population repress by moral restraint, vice, and misery."

Malthus criticized the Poor Laws for leading to inflation rather than improving the well-being of the poor. He supported taxes on grain imports (the Corn Laws). His views became influential and controversial across economic, political, social and scientific thought. Pioneers of evolutionary biology read him, notably Charles Darwin and Alfred Russel Wallace. Malthus's failure to predict the Industrial Revolution was a frequent criticism of his theories.

Malthus laid the "...theoretical foundation of the conventional wisdom that has dominated the debate, both scientifically and ideologically, on global hunger and famines for almost two centuries." He remains a much-debated writer.