Thermodynamic properties of cyclopentanol were studied. The molar heat capacity of c-C5H9OH(cr and l) in the temperature range T = 5.4 K to 303.0 K was measured by vacuum adiabatic calorimetry. Three solid-to-solid transitions were found: at T = 176 K with DtrsHm = (57 2 5) Jโขmol -1 ; at T = 202.6 K with DtrsHm = (3366 2 14) Jโขmol -1 , and at T=234 K with DtrsHm=(5526) Jโขmol -1 . The fusion temperature of c-C5H9OH is 255.6 K, and DfusHm=(122725) Jโขmol -1 . Basic thermodynamic functions at T=298.15 K in the liquid state are Cs, m = (182.48 2 0.73) JโขK -1 โขmol -1 , Sm = (204.14 2 0.90) JโขK -1 โขmol -1 , and Fm = (96.98 2 0.40) JโขK -1 โขmol -1 . The enthalpy of vaporization was measured with a heat-conducting microcalorimeter: DvapHm(298.15 K)=(57.0520.65) kJโขmol -1 . Using these and literature data, the standard molar entropy of c-C5H9OH(g) was determined: Sยฐm(g, 340 K) = (362.9 2 2.4) JโขK -1 โขmol -1 . Conformational analysis was made by the molecular-mechanics method, and statistical calculations of standard molar thermodynamic functions in the ideal-gas state were carried out on the basis of molecular parameters and conformational properties. The calculated entropy value at T=340 K was put into agreement with the experimental one by adjusting the pseudorotational moment of inertia. The standard molar entropy and molar heat capacity of c-C5H9OH in the ideal-gas state at T = 298.15 K are 347.91 JโขK -1 โขmol -1 and 105.43 JโขK -1 โขmol -1 , respectively. Thermodynamic analysis of phase transitions in the condensed state was made. It was shown that pseudorotation in the plastic crystal state of c-C5H9OH is significantly hindered. Thermodynamic quantities allowed us to propose the absence of a non-equilibrium mixture of conformers at T :0. An anomalously low entropy difference between liquid and rigid crystal of cyclopentanol in comparison with other cyclopentane derivatives shows a relatively high ordering in the liquid.