Organisation is a fundamental aspect of any theory simply because it shows how it is applied. If an ideology places organisation to the periphery, then its adherents are not particularly bothered by their stated core principles for it expresses an indifference to whether they are achieved in practice. Like democracy, anarchism saw its task as seeking a form of organisation within which freedom was protected. This chapter reveals that anarchists have spent much time discussing how to organize to meet social needs and achieve their political goals. Showing a marked preference for organizations that are free – voluntary and libertarian – anarchist ideology understands organization in ways that express and expand upon its core concepts. Anarchist organisational principles are core because they intersect with other core concepts by expressing them. Anarchism recognises that there are many types of organization and the chapter describes these types.