Carbon fibers have a diameter of approximately 5 to 10 micrometers . The worldwide demand for carbon fibers has experienced remarkable growth, reaching approximately 150 thousand metric tonnes in 2021, and is predicted to increase at 7.55% CAGR (Compound Annual Growth Rate) until 2035. The high CAGR of carbon fibers occurs because they are lightweight, thermally stable, and have high stiffness and high tensile strength. It has been used in several industries, such as wind, aerospace, automotive, civil, and pressure vessels . Currently, 90% of carbon fibers are based on polyacrylonitrile (PAN), while the remaining 10% are pitch-based, precisely mesophase pitch. Both precursors are petroleum-based. These precursors contribute over 50% of the overall cost of production, making carbon fiber a luxury product . To address this issue, researchers have started to work on various other precursors, such as polyethylene, lignin, and rayon. Table compares the cost per kg of lignin with the total cost of PAN and pitch. The table shows that lignin is a more cost-effective precursor than current carbon fiber precursors. Additionally, it is the only large-volume aromatic renewable feedstock with 60 to 65% carbon content, making it a potential precursor for carbon fibers . Lignin is mainly produced by paper and pulp industries, with a current annual production of 50 to 70 million metric tonnes worldwide, of which less than 2% are utilized to produce value-added products such as formulations of dispersants, binders, and surfactants, and the remainder serve as combustor for heating and power generation . This paper aims to review the chemistry of lignin and the conversion of lignin and lignin-polymer blend into carbon fiber.