The asymmetric unit of the title compound, [K(C(3)H(7)O(3))](n) or K[H(2)gl](n), common name potassium glycerolate, contains half the K(+) cation and half of the glycerolate anion. The other half of the anion is generated through a mirror plane passing through the K atom, and a C, an H and an O atom of the glycerolate ligand. The K(+) ion is coordinated by the O atoms of the OH groups, leading to a six-membered chelate ring that adopts a very distorted boat conformation. The negatively charged O atom of the glycerolate anion, [H(2)gl(-)], is found in the flagpole position and forms an ionic bond with the K(+) ion. The O atoms of the hydroxo groups are coordinated to two K(+) ions, whereas the negatively charged O atom is bonded to one K(+) ion. The K(+) ion is coordinated by three other symmetry-related monodentate H(2)gl(-) ligands, so that each H(2)gl(-) ligand is bonded to two K(+) ions, and the potassium has a seven-coordinate environment. The H(2)gl(-) ligands are connected via a strong O-H⋯O hydrogen bond and, together with the K⋯O inter-connections, form polymeric sheets which propagate in the directions of the a and b axes.