The third edition of the Summer School on Practice and Theory of Distributed Computing (SPTDC 2020) took place on July 6-9, 2020. Because of the ongoing pandemic, the school was held in a virtual format. Following the strategy of the rst and the second editions, we invited prominent researchers working on distributed systems to give lectures on their favourite topics and hold virtual discussions with the students. This year the school pursued three major themes: persistent computing, large-scale replicated systems and cryptographic tools in distributed systems. The program featured classes from Alexey Gotsman, Michael Scott, Christian Cachin, Prasad Jayanti, Idit Keidar, Rodrigo Rodrigues and Jing Chen. We had a record number of 150 registered participants: undergraduate and graduate students, as well as industrial researchers and software engineers from all around the globe.