Innovation is a key driver of economic growth and competitiveness, and innovation clusters house much of the innovation generating high-tech and creative industries. These clusters, as a land use type, evolved overtime in terms of their functions, features, and spatial characteristics. This has led to their reconceptualization from a ‘science and technology park’ model to a ‘innovation district’ model. The key functional and spatial characteristics of innovation districts vary due to the local contextual factors. This makes the determination of the generic typologies of innovation districts challenging, and hence an understudied area of research. This paper aims to expand our understanding on the classification of innovation districts based on their key characteristics. The methodological approach of the study employs a systematic review of the literature on innovation districts, and places global case studies under the microscope. The results point to a holistic approach for the classification of innovation districts through three key factors—(a) Function; (b) Feature, and; (c) Space-use—and their 28 indicators. Each of these factors along with the broader ‘context’, as the fourth one, forms a cornerstone of a conceptual typology framework. The study findings consolidate our understanding on innovation districts, and informs policymaking mechanisms on their planning and development.