Cellulose has sparked considerable interest in the advancement of biodegradable functional materials owing to its abundant natural sources and exceptional biocompatibility. This review offers a comprehensive review of the latest research and development concerning cellulose-based films, with a specific emphasis on their classification, properties, and applications. Specifically, this review classifies cellulose according to the various morphologies of cellulose (e.g., nanocrystals, nanospheres, and hollow ring cellulose) and cellulose derivatives (e.g., methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and cellulose acetate). The subsequent section presents an analysis of cellulose-based films with improved mechanical properties, antibacterial characteristics, gas regulation, and hydrophobicity. A detailed discussion of the mechanisms that underlie these properties is provided. Additionally, representative applications of cellulosic composites, such as food packaging, medical supplies, and electronic devices, are summarized. Finally, the challenges faced by cellulosic materials are outlined, and a novel and feasible prospect is proposed to accelerate the future development of this material.