As an important semiconductor nanomaterial, InP nanowires (NWs) grown with a typical vapor-liquid-solid mechanism are still restricted from their low electron mobility for practical applications. Here, wnonpolaroriented defect-free wurtzite InP NWs with electron mobility of as high as 2000 cm(2) V-1 s(-1) can be successfully synthesized via Pd-catalyzed vapor-solid-solid growth. Specifically, PdIn catalyst particles are involved and found to expose their PdIn{210} planes at the InP nucleation frontier due to their minimal lattice mismatch with nonpolar InP{(2) over bar 110} and {(1) over bar 100} planes. This appropriate lattice registration would then minimize the overall free energy and enable the highly crystalline InP NW growth epitaxially along the nonpolar directions. Because of the minimized crystal defects, the record-high electron mobility of InP NVVs (i.e., 2000 cm(-2) V-1 s(-1) at an electron concentration of 10(17) cm(-3)) results, being close to the theoretical limit of their bulk counterparts. Furthermore, once the top-gated device geometry is employed, the device subthreshold slopes can be impressively reduced down to 91 mV dec(-1) at room temperature. In addition, these NWs exhibit a high photoresponsivity of 10(4) A W-1 with fast rise and decay times of 0.89 and 0.82 s, respectively, in photodetection. All these results evidently demonstrate the promise of nonpolar-oriented InP NWs for next-generation electronics and optoelectronics.