The geometry and style of structural relations at map to microscopic scale on Mykonos, Cyclades, Aegean Sea, Greece, suggests ductile extension and detachment faulting during the late Miocene. This island is dominated by granitic rocks that have a well-developed, shallowly dipping mylonitic foliation and a northeast-southwest-trending mineral elongation lineation. Kinematic indicators in these rocks exhibit a top-to-the-northeast, down-dip sense of shear. Textural relations suggest that conditions during mylonitic deformation were greenschist to amphibolite facies, and published K/Ar geochronology suggests a late Miocene age for this deformation event. Mylonitic rocks lie in the footwall of a low-angle fault, and fault striae parallel to the elongation lineation suggest kinematic coordination between mylonitic deformation and movement along the fault. Translation along the fault juxtaposes younger tilted sedimentary rocks of low metamorphic grade upon the once deeper mylonitic rocks. The style and geometry of deformational fabrics and map relations on this island are strikingly similar to those observed in metamorphic core complexes of the western United States.