Maskless growth of InP wires on planar (100)GaAs substrates by hydride vapor phase epitaxy is demonstrated. The selectivity of the growth was achieved by using focused ion beam to modify locally the substrate surface. The nucleation of deposited InP is enhanced on the exposed areas leading to the selectivity. Continuous 200 μm long wires with submicron cross‐sectional dimensions were obtained in a single growth process. Cross‐sectional transmission electron microscope micrographs show that the number of dislocations in the wires is relatively low, indicating the suitability of the present method for fabrication of nanoscale structures, e.g., quantum wires.