Ecotec (capitalized ECOTEC, from "Emissions Control Optimization TEChnology") is a General Motors (GM) and Opel Automobile GmbH (Opel) trademark that refers to a series of emissions technologies that were implemented throughout a range of GM engines. ECOTEC can refer to the following diesel and petrol engines originally produced by General Motors:

The trademark ECOTEC has also been used on Opel automobiles which are powered by the following engines produced by PSA PowerTrain: