Silicone grease is a waterproof grease made by combining a silicone oil, with a thickener. Most commonly, the silicone oil is polydimethylsiloxane and the thickener is amorphous fumed silica. Using this formulation, silicone grease is a translucent white viscous paste, with exact properties dependent on the type and proportion of the components.

It is commonly used for lubricating and preserving rubber parts, such as O-rings, as it prevents the rubber from drying out. In addition, silicone grease will not swell or soften the rubber, which can be a problem with hydrocarbon based greases. It functions well as a corrosion-inhibitor and lubricant for purposes that require a thicker lubricant, such as the operating mechanism of the M1 Garand rifle.