This thesis explores the representation of subjectivity in the diary films, videos and online projects of Jonas Mekas. In Chapter 1 the intersection of avant-garde and documentary practices are traced to establish that avant-garde filmmakers prioritised subjective representations of the historical world before it became more widely adopted by documentarians. Chapters 2 and 3 then focus on the representation of Mekas' subjectivity in film, while Chapters 4 and 5 focus on video and the Internet. By employing this chronological and technological structure the theoretical and historical debates around subjectivity in film is established in the first three chapters, then re-explored through the prism of new technology. The chapters also operate in pairs that bridge the technological divide to emphasise the different ways that the textual representation of subjectivity is fragmented: Chapters 2 and 4 both focus on the articulation of subjectivity at the moment of shooting, while Chapters 3 and 5 explore the organisation of that material, where new layers of self-inscription are applied. The chapters therefore expand and complicate issues of split subjectivity within new technological frameworks, while remaining focused on attempting to understand Mekas' diary practice.