The ACM CHI Conference on Human Factors in Computing Systems is the premier international conference on Human-Computer Interaction. CHI – pronounced ‘kai’ – is a place where researchers and practitioners gather from across the world to discuss the latest in interactive technology. CHI is generally considered the most prestigious in the field of HCI and attracts thousands of international attendees annually. CHI will be held for the first time in Japan, in the city of Yokohama, just south-west of Tokyo. In 2021 our conference will be a hybrid conference event, and our theme encourages authors and delegates to make waves as they feature the latest discoveries and advances in HCI and shake up the existing state of affairs. And to think of CHI as a platform to combine strengths of different people from different perspectives. This gives rise to our CHI 2021 theme "Making Waves, Combining Strengths".