The stoichiometry of single ternary III–V semiconductor nanowires was analyzed by Raman spectroscopy. Free‐standing AlxGa1−xAs nanowires were obtained through metal organic vapor phase epitaxy (MOVPE) by the vapor liquid solid (VLS) mechanism on GaAs substrates. The as‐grown nanowires were studied with a scanning confocal Raman spectrometer (spatial resolution ≈300 nm). They were located by Rayleigh imaging and individual nanowires selected for Raman spectroscopy. The acquired spectra exhibit 2‐mode behavior. The stoichiometry of single nanowires was determined based on the frequencies of the GaAs‐ and AlAs‐like transversal optical (TO) and longitudinal optical (LO) peaks with an accuracy of below 10%. Measurements at different positions along the axis revealed variations of the composition within single nanowires. This non‐uniformity evidences that the nanowires possess an …