1,2,3,4,5-Cyclopentanepentol, also named cyclopentane-1,2,3,4,5-pentol or 1,2,3,4,5-pentahydroxycyclopentane is a chemical compound with formula C5H10O5 or (–CHOH–)5, whose molecule consists of a ring of five carbon atoms (a cyclopentane skeleton), each connected to one hydrogen and one hydroxyl group.

However it is very rarely found in nature, and therefore it has received much less attention than the ubiquitous six-carbon version, inositol.

The conversion between 1,2,3,4/5 and 1,2,3/4,5 is faster and entails the hydrogen and hydroxyl switching places on either of the two carbon atoms located between an "α" and a "β" position.

[10] Mass spectrometry of the compound generates mainly the ion HO–CH=CH=CH=O+H (mass-charge ratio 73) and a neutral radical C2H5O•.

[3] Trteatment of the derivative 3,4,5-tri-O-acetyl-1,2-O-ethylidene-(1,2,4/3,5)-cyclopentanepentol with triphenylcarbenium tetrafluoroborate [(C6H5)3C]+[BF4]− to yield the cation 3,4,5-tri-O-acetyl-(1,2,4/3,5)-cyclopentanepentol-1,2-O-acetoxonium, which exhibits a peculiar 10-stage cyclic rearrangement.

[13] The related compound 1,2,3,4,5-pentakis(hydroxymethyl)-cyclopentane (a colourless viscous oil, soluble in tert-butanol and DMSO) was synthesized in 1985 by L. M. Tolbert and others.

[23] Trace amounts of cyclopentanepentol were identified in some plants, such as the red flower calyces of Hibiscus sabdariffa (roselle);[24] the plant Maclura pomifera (Osage orange);[25] and the cyanobacterium Oscillatoria willei[26] as well as in the products of its hydropyrolysis.