Liquid paraffin, also known as paraffinum liquidum, paraffin oil, liquid paraffin oil or Russian mineral oil, is a very highly refined mineral oil used in cosmetics and medicine. Cosmetic or medicinal liquid paraffin should not be confused with the paraffin (i.e. kerosene) used as a fuel. The generic sense of paraffin meaning alkane led to regional differences for the meanings of both paraffin and paraffin oil. It is a transparent, colorless, nearly odorless, and oily liquid that is composed of saturated hydrocarbons derived from petroleum.

The term paraffinum perliquidum is sometimes used to denote light liquid paraffin, while the term paraffinum subliquidum is sometimes used to denote a thicker mineral oil.