The third edition of Prague Summer School on Discrete Mathematics will be held on August 24-28, 2020 in the historical building of the Computer Science Department of Charles University in the very heart of Prague. Lecture series will be given by Subhash Khot (New York University) and Shayan Oveis Gharan (University of Washington). The School is primarily intended for PhD students and early career researchers. There is no registration fee and a number of travel stipends will be available.