The Ninth International Conference on Human-Agent Interaction (HAI 2021, in cooperation with ACM SIGCHI) aims to be the premier interdisciplinary venue for discussing and disseminating state-of-the-art research and results that have implications across conventional interaction boundaries including robots, software agents and digitally-mediated human-human communication. The theme for HAI 2021 will be “Distributed Together, Making Connections”. Due to the pandemic, we have been forced to disperse physically. As a result, online video conferencing and communication through social networking services are becoming more popular. Agents and avatar systems that mediate and extend human society may help us to overcome this isolation. Such systems could contribute by helping us to make connections while we are apart from each other. While all submissions related to HAI are welcome, you are especially encouraged to submit papers in line with the theme for HAI 2021. The HAI conference seeks contributions from a broad range of disciplines such as engineering, computer science, psychology, sociology, cognitive science, business, marking and design. We hope to be a venue to connect these diverse areas, even though the conference will be online.