The molecular structure of 2-trifluoromethylphenol has been determined by gas-phase electron diffraction. The analysis, aided by constraints from ab initio molecular orbital calculations, yielded the following bond lengths (r(g)) and bond angles : (C-C)(Ar,mean), 1.395 +/- 0.004 Angstrom; C-C(F-3), 1.510 +/- 0.005 Angstrom; C-O, 1.362 +/- 0.011 Angstrom; (C-F)(mean), 1.358 +/- 0.006 Angstrom; angle O-C-1-C-2, 121.0 +/- 1.2 degrees; angle C-O-H, 105 +/- 6 degrees; angle C(F-3)-C-2-C-1, 120.7 +/- 0.8 degrees; (C-C-F)(mean), 113.2 +/- 0.3 degrees; CF3 torsion, 10.1 +/- 0.8 degrees. Weak intramolecular bifurcated hydrogen bonding between the hydroxy hydrogen and two of the CF3 fluorines is indicated by the H ... F nonbonded distances 2.05 +/- 0.06 and 2.42 +/- 0.06 Angstrom. Compared with the freely rotating CF3 group in trifluoromethylbenzene, the well-defined conformer of 2-trifluoromethylphenol indicates the constraining effect of hydrogen bonding.