After the successful conferences on Diophantine m-tuples and related problems on November 2014 and October 2018, we are happy to announce that the third conference on the same topic (Diophantine m-tuples and related problems III) will take place at Faculty of Civil Engineering, University of Zagreb, Croatia, from September 23 to September 25, 2020. The conference will be dedicated to Diophantine m-tuples and related problems. However, other aspects of Diophantine equations may appear as well. Anybody wishing to attend is welcome to contact the organizers.