Ecological economics is a branch of economic theory, also known as human development theory or natural welfare economics, that assumes an inherent link between the health of ecosystems and that of human beings. It is sometimes referred to as "Green Economics" and thematically is a major challenge to the present global capitalist economic paradigm in its radical restatement of the views of green economists or the more conventional environmental economics to more directly challenge the classical ideas of growth or optimality.

The primary argument of ecological economics that sets its apart from previous economic theory is that economics is itself a strict subfield of ecology, in that ecology deals with the energy and matter transactions of life and the earth, and the human economy is by definition contained within this system. Chief among the critiques of current normative economics by ecological economists is its approach to natural resources and capital. Analyses from the standpoint of conventional and environmental economics undervalue natural capital in that it is treated as a factor of production interchangeable with labor and technology (human capital). It is claimed that human capital is complementary to natural capital rather than interchangeable, as human capital inevitably derives from natural capital in one form or another. It rejects the view of energy economics that growth in the energy supply is related directly to well being, focusing instead on biodiversity and creativity - or natural capital and individual capital, in the terminology sometimes adopted to describe these economically. In practice, ecological economics focuses primarily on the key issues of uneconomic growth and measuring well-being. Ecological economists are inclined to acknowledge that much of what is important in human well-being is not analyzable from a strictly economic standpoint and suggests interdisciplinarity with social and natural sciences as a means to address this.

The origination of ecological economics as a specific field per se is credited to ecologist and University of Vermont Professor Robert Costanza, who founded the International Society for Ecological Economics and carried out much of the founding research while at the University of Maryland. His University of Maryland colleague Herman Daly as significantly contributed to its development. Ecological economics' intellectual ancestor may be traced in large part to political economy, a refinement of early economic theory that includes among its earlier researchers the Rev. Thomas Malthus, David Ricardo, and Karl Marx. CUNY geography professor David Harvey was one of the first to explicitly add ecological concerns to political economic literature. This parallel development in political economy has been continued by analysts such as sociologist John Bellamy Foster.