This article presents the first consensus-based definition of early health technology assessment (HTA): “an HTA conducted to inform decisions about subsequent development, research, and/or investment by explicitly evaluating the potential value of a conceptual or actual health technology.” The definition was developed and refined through the involvement of relevant stakeholders in the field, a working group, and a survey panel, aiming to reach a consensus. An important part of this work was distinguishing between early HTA and related concepts, such as early awareness, dialogue, and scientific advice; thus, clarifying its unique role in HTA. Furthermore, the authors discuss how early HTA may guide investment decisions in development and reduce research waste. In addition, the consensus-based definition may enhance clarity for developers in producing early decision support to reach healthcare providers and policymakers. Finally, the article emphasizes the need for standardized terminology to increase the visibility of research, development, and policy in early HTA.