Lignin, one of the most abundant biopolymers on Earth, has emerged as a promising material for multifunctional applications utilizing 3D printing techniques. As a low-cost and underutilized by-product of the pulp and paper industry, lignin offers an attractive alternative to petroleum-derived polymers that are commonly used in 3D printing applications. This chapter discusses the integration of lignin into 3D printing technologies, providing a comprehensive overview of the processing, properties, and applications of lignin-based systems. The chapter begins with an introduction to the biodegradability and chemical versatility of lignin, and its extraction, purification, various chemical modifications and blends. Next, we review its compatibility with various 3D printing techniques, such as fused filament fabrication (FFF), stereolithography (SLA), and direct ink writing (DIW). The printability challenges of utilizing lignin as a standalone material with each of these techniques are highlighted. The various approaches to enhance printability through blends with other polymers and rheology modifiers are discussed. The potential of lignin-cellulose composites is also explored, highlighting their synergistic properties for 3D printing. Our works on 3D printing of wood from lignin and cellulose combination via DIW technique of a water-based ink and enhancing their mechanical properties with natural fiber reinforcements are described. Finally, the chapter concludes with applications and possible future directions. Overall, this chapter underscores the transformative role of 3D printing in valorizing the abundant biopolymer lignin.