Abstract: It is our great pleasure to welcome you to the 18th IFIP TC13 International Conference on Human-Computer Interaction, INTERACT 2021, one of the most important conferences in the area of Human-Computer Interaction at a world-wide level.INTERACT 2021 was held in Bari (Italy) from August 30 -September 3, 2021, in cooperation with ACM and under the patronage of the University of Bari Aldo Moro.This is the second time that INTERACT was held in Italy, after the edition in Rome in September 2005.The Villa Romanazzi Carducci Hotel, which hosted INTERACT 2021, provided the right context for welcoming the participants, thanks to its liberty-period villa immersed in a beautiful park.Due to the COVID-19 pandemic, INTERACT 2021 was held in hybrid mode to allow attendees who could not travel to participate in the conference.INTERACT is held every two years and is well appreciated by the international community, attracting experts with a broad range of backgrounds, coming from all over the world and sharing a common interest in HCI, to make technology effective and useful for all people in their daily life.The theme of INTERACT 2021, "Sense, Feel, Design," highlighted the new interaction design challenges.Technology is today more and more widespread, pervasive and blended in the world we live in.On one side, devices that sense humans' activities have the potential to provide an enriched interaction.On the other side, the user experience can be further enhanced by exploiting multisensorial technologies.The traditional human senses of vision and hearing and senses of touch, smell, taste, and emotions can be taken into account when designing for future interactions.The hot topic of this edition was Human-Centered Artificial Intelligence, which implies considering who AI systems are built for and evaluating how well these systems support people's goals and activities.There was also considerable attention paid to the usable security theme.Not surprisingly, the COVID-19 pandemic and social distancing have also turned the attention of HCI researchers towards the difficulties in performing user-centered design activities and the modified social aspects of interaction.With this, we welcome you all to INTERACT 2021.Several people worked hard to make this conference as pleasurable as possible, and we hope you will truly enjoy it.