Arrays of well-aligned AlN nanowires (NWs) with tunable p-type conductivity were synthesized on Si(111) substrates using bis(cyclopentadienyl)magnesium (Cp(2)Mg) vapor as a doping source by chemical vapor deposition. The Mg-doped AlN NWs are single-crystalline and grow along the [001] direction. Gate-voltage-dependent transport measurements on field-effect transistors constructed from individual NWs revealed the transition from n-type conductivity in the undoped AlN NWs to p-type conductivity in the Mg-doped NWs. By adjusting the doping gas flow rate (0-10 sccm), the conductivity of AlN NWs can be tuned over 7 orders of magnitude from (3.8-8.5) × 10(-6) Ω(-1) cm(-1) for the undoped sample to 15.6-24.4 Ω(-1) cm(-1) for the Mg-doped AlN NWs. Hole concentration as high as 4.7 × 10(19) cm(-3) was achieved for the heaviest doping. In addition, the maximum hole mobility (∼6.4 cm(2)/V s) in p-type AlN NWs is much higher than that of Mg-doped AlN films (∼1.0 cm(2)/V s). (2) The realization of p-type AlN NWs with tunable electrical transport properties may open great potential in developing practical nanodevices such as deep-UV light-emitting diodes and photodetectors.