A silicone oil is any liquid polymerized siloxane with organic side chains.

Silicone oils are primarily used as lubricants, thermionic fluid oils or hydraulic fluids. They are excellent electrical insulators and, unlike their carbon analogues, are non-flammable. Their temperature stability and good heat-transfer characteristics make them widely used in laboratories for heating baths (“oil baths”) placed on top of hotplate stirrers, as well as in freeze-dryers as refrigerants.