Mafic is an adjective describing a silicate mineral or igneous rock which is rich in magnesium and iron. The term is a portmanteau, made up from "magnesium" and "ferric".

Mafic minerals are usually dark in color and have a specific gravity greater than 3. Common rock-forming mafic minerals include olivine, pyroxene, amphibole, biotite and other micas, augite and the calcium-rich plagioclase feldspars. Common mafic rocks include basalt and gabbro.