The Delphi technique has established itself in health research as a valuable method for developing strategies and standards on which consensus can be reached and exploring potential future scenarios based on expert knowledge. Originally introduced in the 1950s by the RAND Corporation for military foresight, it is now increasingly used in health research. Characteristic of Delphi studies is the iterative process of surveying a group of experts by means of standardized questionnaires and giving controlled feedback. Experts can be scientists, practitioners, or even those affected, which allows for a wide range of perspectives and makes the results more robust and practical. The methodological basis for the technique includes structured communication processes and the anonymity of the respondents in order to enable the formation of judgments free of external pressure. The typical process of a Delphi study is sequentially divided into preparation, survey, analysis, and reporting and dissemination. The preparation phase is used to define objectives and relevant content, secure resources, and put together a suitable panel of experts. The survey phase consists of at least two rounds in which the experts are questioned and given feedback. During the analysis phase, data are evaluated to ascertain consensus or dissent, while dissemination and reporting involve the publication of the results. The Delphi technique has a wide range of application especially in healthcare, for example, assessing epidemiological trends, developing guidelines and recommendations for action, and identifying innovative scenarios and technological developments. Variants of the classic Delphi technique, such as the real-time Delphi and the policy Delphi, as well as modified approaches, enable flexible adaptation to different research questions. Despite criticism concerning the lack of standardization and absence of reflection on the various modifications, the Delphi technique displays great potential for inter- and transdisciplinary collaboration and for answering complex questions in the health sciences. This chapter provides an overview of Delphi techniques in the health sciences, lays out the methodological principles, explains the main steps of a Delphi study, and identifies variants and relevant areas of application. Presented as an example is a Delphi study aimed at establishing consensus on the definitions and terminology of developmental language disorders, followed by a summary of the opportunities and challenges that the Delphi technique poses.