Abstract: Lignin, a renewable and eco-friendly biomass resource, is rich in reactive functional groups (e.g., phenolic hydroxyl and carboxyl groups) in its molecular structure and features inherent antioxidant, antimicrobial, and UV-shielding properties. These characteristics provide a critical basis for developing functional 3D-printed hydrogels. In turn, 3D printing technology enables the precise structural design and controllable fabrication of hydrogels, offering a new route to advance them toward high-performance, customized, and sustainable development. This paper systematically reviews the main 3D-printed preparation technologies for lignin composite hydrogels, including photocuring 3D printing, direct ink writing, and micro-extrusion 3D bioprinting, and analyzes the roles and functions of lignin in different printing ink systems. On this basis, it summarizes the application status of 3D-printed lignin composite hydrogels in biomedicine, flexible sensors, intelligent responsive materials, and other fields. Finally, the challenges and future development directions of lignin in 3D-printed hydrogels are prospectively discussed.