来苏糖是一种戊醛糖，在自然界罕见。例如，细菌糖脂质的成分就含有来苏糖。

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.

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