Self-determination theory (SDT) has been widely successful in HCI. It offers ready concepts, measures, and theoretical propositions for third wave HCI topics like user experience, fun, wellbeing, motivation, or user autonomy. Still, HCI applications of SDT have been partial, at times superficial, and disconnecting – leaving great unfulfilled potential which motivated the present special issue. In this introduction, we present SDT to interested scholars; chart its use across HCI to date; and outline six advances to move HCI toward more intentional applications of SDT. As the articles from this issue illustrate, future growth areas of SDT in HCI are in extending domain-specific models and applications; harnessing underused parts of theory; computational formalisation; extending levels of analysis; facilitating design translation; and engaging in a cross-disciplinary dialogue on autonomy.