IJCAI-PRICAI-20 is a conference we will long remember as one that involved many firsts. This year was the first time that IJCAI and the Pacific Rim International Conference on Artificial Intelligence have been held jointly. This was the first time that an IJCAI conference has been held in a year other than its name: IJCAI-PRICAI-20 was in fact held on January 7-15, 2021. And of course, this was the first virtual IJCAI. In March 2020, the conference committee realized that the COVID-19 pandemic might well affect travel plans and that we would need to prepare for several contingencies. It quickly became apparent that we would not be able to hold IJCAI in July 2020 as originally scheduled-and as we monitored the evolving pandemic, it gradually became clear that it would not be possible to hold an in-person conference at all. With a tremendous "second shift" of planning by the conference committee and all of the track chairs, and in cooperation with VirtualChair, we were able to design and launch a fully online, immersive conference experience. AI has burgeoned in recent years, and the pace of development of AI-related technologies has only accelerated in response to the pandemic, with entire industries rapidly moving to a virtual work environment. Alongside the growth of AI technology has come a growing interest in AI ethics and social impact, with an increased recognition that AI has the capacity to change the human trajectory for good, but also the capacity to reinforce and increase existing inequities. IJCAI-PRICAI-20 follows a long tradition of deep attention to both technology and ethical issues, incorporating a topical track on, special tracks on AI in FinTech (Financial Technology) and Computational Sustainability and Human Well-Being, panels on Women in AI and Diversity in AI, and a special roundtable on AI Futures: Report from the One Hundred Year Study on Artificial Intelligence (AI100). IJCAI-PRICAI-20 received a record number of 5,680 submitted papers (an 20% increase over IJCAI-19, itself a record breaker), of which 704 submissions were accepted (12.4%). The initial screening phase identified 343 papers for desk rejection due to violations of the submission requirements. To manage the increasing load of reviewing, this year we introduced a summary reject phase in the main track, in which 2,191 of the remaining 4,804 main-track papers (46%) were rejected using an accelerated review process. Almost all of the remaining 2,613 papers received four reviews. The special track on Sustainability and Human Well-being and the special track on AI for FinTech received 96 and 188 papers, respectively, of which 19 and 35 were accepted (respectively). In the virtual format, all papers included a recorded oral presentation, a live Q&A session, and a virtual poster presentation. The Program Committee consisted of 5 associate program chairs, 92 area chairs, 925 senior program committee members, 4,130 program committee members, and 83 external reviewers, for a total of 5,235 researchers who performed careful and rigorous reviews, discussed the papers, and made final recommendations. In the full review phase, authors had the opportunity to provide feedback to their reviews, which was then analyzed by the reviewing team at the time of discussion. The journal track includes 29 abridged versions of papers that have been published in AIJ and JAIR without having ever been presented at a major conference. The sister conference best paper track includes 21 revised versions of award-winning papers from some of the top-level specialized AI conferences. 14 early career spotlight talks were given by outstanding researchers who are 5 to 10 years past their doctorate. The survey track provides an opportunity for AI researchers who are experts on a specific topic to give a talk presenting a synthesis survey of the topic and to publish a paper in the proceedings. We