Ferrosilicon, or ferrosilicium ( FeSi ), is a ferroalloy, an alloy of iron and silicon. It contains a high proportion of iron silicides. Its melting point is about 1200 °C.

Ferrosilicon is used in steelmaking and foundries as a source of silicon in production of carbon steels, stainless steels, and other ferrous alloys for its deoxidizing properties, to prevent loss of carbon from the molten steel. Ferrosilicon is also used for manufacture of silicon. In manufacture of cast iron, ferrosilicon is used for inoculation of the iron to accelerate graphitization. In arc welding, ferrosilicon can be found in some electrode coatings.

Lumpy, basis 75% Si (Scale Pro rata), min. 75%