The melting temperatures of nine n-alkylbenzenes (undecylbenzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene, pentadecylbenzene, hexadecylbenzene, heptadecylbenzene, octadecylbenzene, and nonadecylbenzene) were measured by means of a high-pressure microscope up to 100 MPa. The experimental device used in this work allowed the distinction between stable and metastable solid phases. The influences of the alkyl chain length and pressure on the melting temperatures of the stable solid phases are discussed.