Ecotax (short for Ecological taxation) refers to taxes intended to promote ecologically sustainable activities via economic incentives. Such a policy can complement or avert the need for regulatory (command and control) approaches. Often, an ecotax policy proposal may attempt to maintain overall tax revenue by proportionately reducing other taxes (e.g. taxes on human labor and renewable resources); such proposals are known as a green tax shift towards ecological taxation.

Ecotaxes are examples of pigovian taxes, which are taxes that attempt to make the private parties involved feel the social burden of their actions.