Thomas Robert Malthus was an English economist and demographer who lived from 1766 to 1834. He is best known for his theory of population growth, which he outlined in his 1798 work "An Essay on the Principle of Population." Malthus argued that population tends to grow at a faster rate than the means of subsistence, leading to poverty and misery. This theory became known as the "Malthusian theory" and had a significant impact on the fields of economics, sociology, and public policy. Malthus's work continues to be influential in discussions about population growth, resource scarcity, and sustainable development.