We present ATOMIC 2020, a commonsense knowledge graph with 1.33M everyday inferential knowledge tuples about entities and events. ATOMIC 2020 represents a large-scale common sense repository of textual descriptions that encode both the social and the physical aspects of common human everyday experiences, collected with the aim of being complementary to commonsense knowledge encoded in current language models. ATOMIC 2020 introduces 23 commonsense relations types. They can be broadly classified into three categorical types: 9 commonsense relations of social-interaction, 7 physical-entity commonsense relations, and 7 event-centered commonsense relations concerning situations surrounding a given event of interest.