In recent years, various nanomaterials, particularly bio-based nanomaterials, have gained attention as innovative approaches to improve conventional papers and develop advanced products. Owing to their renewable origin, biodegradability, and ability to impart multifunctional properties, these materials play a significant role in developing sustainable products for the paper industry. Among these materials, nanocelluloses, including cellulose nanofibers (CNFs), lignocellulosic nanofibers (LCNFs), cellulose nanocrystals (CNCs), and bacterial nanocellulose (BNC), have received the greatest attention and application. Among them, CNFs with high purity and transparency serve as effective reinforcing agents for high-strength papers and bio-based coatings; however, their high production energy demand and moisture sensitivity remain major limitations. In contrast, LCNFs offer advantages such as reduced production cost and energy consumption, along with improved resistance to moisture and ultraviolet (UV) radiation, making them promising candidates for sustainable packaging applications and biorefinery-based systems. CNCs and BNC also exhibit great potential in the production of advanced papers due to their high crystallinity, excellent mechanical properties, and ability to form well-organized nanostructures. In addition to nanocelluloses, lignin nanoparticles and nanochitosan are among the other important bio-based nanomaterials used in papermaking. Lignin nanoparticles enable the production of functional papers through their UV-absorbing capacity, antioxidant activity, and ability to improve moisture resistance, whereas nanochitosan, owing to its biocompatibility and antimicrobial properties, is suitable for hygienic applications and the development of active and intelligent packaging papers. Overall, the rational combination of these nanomaterials can provide a pathway toward the development of next-generation papers with advanced mechanical, barrier, and functional properties.