This article aims to propose a taxonomy of theoretical approaches in implementation science, distinguishing between different categories of theories, models, and frameworks to facilitate the selection and application of relevant methods in research and practice. The three overarching aims of these theoretical approaches are described: (1) describing and/or guiding the process of translating research into practice, (2) understanding and/or explaining what influences implementation outcomes, and (3) evaluating implementation. The article identifies five categories of theoretical approaches: process models, determinant frameworks, classic theories, implementation theories, and evaluation frameworks. Each category has distinct characteristics and focuses, with some overlap between them. Process models guide the translation of research into practice, while determinant frameworks identify barriers and enablers that influence implementation outcomes. Classic theories from fields like psychology and sociology are used to explain change mechanisms, and implementation theories are developed to enhance understanding of specific aspects of implementation. Evaluation frameworks provide a structure for assessing implementation efforts. The article emphasizes the importance of recognizing the differences between these categories to facilitate appropriate selection and application of relevant approaches in implementation research and practice.This article aims to propose a taxonomy of theoretical approaches in implementation science, distinguishing between different categories of theories, models, and frameworks to facilitate the selection and application of relevant methods in research and practice. The three overarching aims of these theoretical approaches are described: (1) describing and/or guiding the process of translating research into practice, (2) understanding and/or explaining what influences implementation outcomes, and (3) evaluating implementation. The article identifies five categories of theoretical approaches: process models, determinant frameworks, classic theories, implementation theories, and evaluation frameworks. Each category has distinct characteristics and focuses, with some overlap between them. Process models guide the translation of research into practice, while determinant frameworks identify barriers and enablers that influence implementation outcomes. Classic theories from fields like psychology and sociology are used to explain change mechanisms, and implementation theories are developed to enhance understanding of specific aspects of implementation. Evaluation frameworks provide a structure for assessing implementation efforts. The article emphasizes the importance of recognizing the differences between these categories to facilitate appropriate selection and application of relevant approaches in implementation research and practice.