An imaging spectrometer with adaptive space-variant spectral resolution is introduced to improve spectrometer data collection efficiency. Pixel-based dynamically selectable dispersion is achieved using microelectromechanical system (MEMS) mirrors to control the light path of each image point through the spectrometer. A compact (1 x 4 x 0.3 mm) planar-optics structure is demonstrated, allowing the tiling of multiple spectrometers in an array for large image formats. The prototype spectrometer covers a wavelength between 500 and 1000 nm with a spectral resolution that is dynamically adaptable for each pixel from 7.5 to 15 nm.