Altrose is an aldohexose sugar. <small>D</small>-Altrose is an unnatural monosaccharide. It is soluble in water and practically insoluble in methanol. However, L-altrose has been isolated from strains of the bacterium Butyrivibrio fibrisolvens.
Altrose is a C-3 epimer of mannose. The ring conformation of ñ-altropyranoside is flexible compared to most other aldohexopyranosides, with idose as exception. In solution different derivatives of altrose have been shown to occupy both <sup>4</sup>C<sub>1</sub>, <sup>O</sup>S<sub>2</sub> and <sup>1</sup>C<sub>4</sub>-conformations.