Syn- to late-orogenic extension caused by gravitational collapse is a process that has been documented in most orogens. In this paper, we investigate the contemporaneous stress field in Taiwan to examine syn-orogenic extensional faulting and the possible gravitational collapse modes by which it is taking place. We use a large, well-constrained, clustered earthquake focal mechanism data set from which we calculate the contemporaneous stress field (σ1, σ2, σ3), the direction of the maximum compressive horizontal stress (SH), and determine the most likely fault plane orientations and kinematics. Our results show that, in the upper 21 km of the crust, shearing, with lesser compression are the dominant stress regimes in the Western Foothills and Hsuehshan Range, resulting in a complex interaction of strike-slip (with transpression and transtension) and thrust faulting. Extension is predominately localised in the upper 14 km of the crust in the Central Range, where it is roughly orogen-parallel. SH and the best-fit fault planes in the Central Range strike roughly NW-SE, at a high angle to the structural and topographic grain. At depths greater than 21 km, compression and shear (with transpression and minor extension) are the dominant stress regimes throughout Taiwan. Along the eastern flank of the mountain belt, mixed compression and shear stress regimes at depths greater than 50 km are related to the Manila and Ryukyu subduction zones. Our results suggest that Taiwan is undergoing orogen-parallel extension as a result of lateral extrusion with free-boundary gravitational collapse.