The Oshima metamorphic complex, which is located on Oshima Island, western Ehime, Shikoku Island, is a rare high-temperature metamorphic complex in the outer belt of Southwest Japan. The complex and accompanying granitic mylonites were subjected to zircon U-Pb age dating by LA-ICP-MS and monazite U-Th-Pb chemical age dating by FE-EPMA. The complex yields detrital zircon ages of ca. 2000-140 Ma and might have undergone a main high-temperature metamorphism at ca. 120 Ma, intrusion by gabbroic to tonalitic magma at ca. 110 Ma, and brittle deformation associated with pseudotachylite formation at ca. 100 Ma. In contrast, the granitic mylonites were possibly derived from the felsic magmatism at ca. 170 Ma, indicating an origin independent from that of the Oshima metamorphic complex. The geology and geochronology of the complex are similar to those of the Higo metamorphic complex and possibly comparable with the Atokura nappes in the Kanto mountains, and the Takanuki and Nishidohira metamorphic rocks of the Abukuma plateau. The results indicate the presence of a large-scale Cretaceous plutono-metamorphic complex extending from Kyushu to the south Tohoku area.