This chapter explores the related ideas of access to knowledge resources and shared governance of those resources, often known as commons. Knowledge resources consist of many types and forms. Some are tangible, and some are intangible. Some are singular; some are reproduced in copies. Some are singular or unique; some are collected or pooled. Some are viewed, used or consumed only by a single person; for some resources, collective or social consumption is the norm. Any given resource often has multiple attributes along these dimensions, depending on whether one examines the resource’s physical properties, its creative or inventive properties, or its natural, factual or ideational properties. Access questions are, accordingly, diverse. That diversity is compounded by the proposition that access is itself a property of a resource, in the sense that resource characteristics are, to a substantial extent, socially and culturally constructed. Social construction means not only that boundaries among properties of a resource may be blurred but also that those properties and boundaries may change over time. By virtue of that diversity, investigating access to knowledge resources creates the risk of producing a conceptually fragmented and unhelpful landscape of theory and application on a resource-by-resource basis. This chapter suggests that the investigation of access to knowledge resources may be unified under the umbrella concept of knowledge commons, the study of governance of shared knowledge resources. It presents a framework for understanding knowledge commons and illustrates its application to several questions of access to the material and immaterial dimensions of specific knowledge resources.