Cellulose nanofiber (CNF) has emerged as a sustainable and functional biomaterial for additive manufacturing, offering a unique combination of biodegradability, mechanical strength, and tunable surface chemistry.Among various bio-derived materials, CNF is particularly well suited for 3D printing due to their suitable rheological behavior, including shear thinning, yield stress, thixotropic recovery, and viscoelasticity.These properties enable precise control over ink flow and shape fidelity, which are essential for constructing complex structures across a range of printing techniques such as direct ink writing (DIW), embedded 3D printing, and stereolithography (SLA).This review presents a comprehensive overview of the formulation, rheological characterization, and printability of CNF inks, emphasizing how processing conditions collectively influence printability.Representative applications of CNF inks are discussed, including biofabrication, soft electronics, and microfluidic devices, with a focus on how ink design translates to structural performance and functional integration.Finally, this review outlines key challenges and future directions in the development of CNF inks, emphasizing their potential as foundational materials for sustainable and high-precision additive manufacturing.