Flexible and conformable organic single crystals as thin as 150 nm are used for fabricating mechanically bendable organic single-crystal field-effect transistors on low-cost plastic substrates (see figure and cover). We report effective field-effect mobility as high as 4.6 cm(2) V-1 s(-1) for a flexible rubrene single-crystal transistor, on/off ratio of ca. 106, threshold voltage of - 2.1 V, and a normalized subthreshold swing of 0.9 V nF decade(-1) cm(-2).