环戊五酮也称为“五酮环戊烷”或“白酮酸”，是一种有机碳氧化物，其分子式为C₅O₅。这种化合物可看作是环戊烷的五羰基取代物或一氧化碳的五聚物。

直至2000年，环戊五酮的大量合成仍未实现，但已有微量合成的报道。

现在市面上以“五水合环戊五酮”（C₅O₅·5H₂O）为名进行销售的化学试剂可能实为十羟基环戊烷（C₅(OH)₁₀）。

Cyclopentanepentone, also known as leuconic acid, is a hypothetical organic compound with formula C₅O₅, the fivefold ketone of cyclopentane. It would be an oxide of carbon (an oxocarbon), indeed a pentamer of carbon monoxide.

As of 2000, the compound had yet to be synthesized in bulk, but there have been reports of trace synthesis.