Lyxose is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. It has chemical formula C₅H₁₀O₅. It is a C'-2 carbon epimer of the sugar xylose. The name "lyxose" comes from reversing the prefix "xyl" in "xylose".

Lyxose occurs only rarely in nature, for example, as a component of bacterial glycolipids.