This proceedings volume contains papers presented during the conference on Remote Sensing for Agriculture, Ecosystems, and Hydrology XIII. The conference was part of the 18th International Symposium on Remote Sensing sponsored by SPIE—The International Society for Optical Engineering. The symposium was held at the Clarion Congress Hotel Prague, Prague, Czech Republic, from 19th to 21th of September 2011. The conference is dedicated to providing rapid dissemination of scientific and technical information, and attracted scientists and professionals from throughout Europe, Africa, Asia, and the Americas. Approximately 45 oral and 30 poster presentations were given, covering a broad range of topics in the field of remote sensing applications in environmental science. The program was organized according to major themes, with 10 sessions on Agriculture: Irrigation and Energy Balance and Agriculture (2); Ecosystems: Estuarine, Coastal and Inland Waters; Vegetation and Change detection; Hydrology: Snow and Hydrology (2). The poster presentations also had good representation from the abovementioned themes. The presentations described both fundamental and applications-based research activities from modelling, to laboratory and field experiments, to operational applications. The oral program also included three invited presentations: James L. Foster of NASA Goddard Space Flight Ctr. (USA) gave a presentation on the subject “Remote sensing of snow cover and snow water equivalent for the historic snowstorms in the Baltimore/Washington area during February 2010” within a Snow session; Heikki K. Saari of VTT Technical Research Ctr. of Finland (Finland) gave a presentation on the subject “Unmanned aerial vehicle (UAV) operated spectral camera system for forest and agriculture applications” within General Application session; Clement Atzberger of University of Natural Resources and Life Sciences (BOKU) Wien, (Austria) gave a presentation on the subject “Why confining to vegetation indices? Exploiting the potential of improved spectral observations” within a Vegetation session; Short reports pointing out the state of art and perspectives in the research fields of the invited talks are reported below. We extend our thanks to the co-editor Katja Richter of Ludwig-Maximilians-Univ. München, and Session chairs Francesco Vuolo of Univ. of Univ. für Bodenkultur Wien (Austria) and Goffredo La Loggia of Univ. degli Studi di Palermo, and to the presenters for their efforts and to the participants for their insightful questions and discussions. Special thanks are also due to the host city for the excellent venue and to all the SPIE organizational staff for their support prior to, during, and after the symposium. We look forward to an even more successful conference in 2012.