<p>Synthetic polymers are integral to modern society; however, their non-biodegradable nature has resulted in the accumulation of persistent plastic waste, posing significant environmental and ecological threats. The substantial carbon footprint associated with their cradle-to-grave lifecycle underscores the urgent need to transition toward degradable, bio-based polymers and biocomposites. Natural, biodegradable polymers, such as polysaccharides (e.g., cellulose, chitin, alginate) and proteins (e.g., collagen, gelatin, silk), offer viable solutions to address plastic pollution and mitigate climate change, aligning with global efforts to achieve a Net Zero society. This review comprehensively examines current biopolymeric systems, their feedstocks, chemical functionalities, and the role of additives in enhancing their properties. It highlights the development of biocomposites, which combine biopolymers with natural or synthetic reinforcements to improve mechanical, thermal, and functional performance. Key applications in packaging, healthcare, and tissue engineering are discussed, along with advanced manufacturing methods such as 3D printing, electrospinning, and extrusion. By bridging the gap between fundamental research and practical applications, this review provides insights into the potential of biopolymers and biocomposites as sustainable alternatives to conventional synthetic polymers, paving the way for a circular economy and reduced environmental impact.</p>