<p>Agricultural production generates substantial quantities of organic residues, including husks, hulls, bran, pomace, stalks, and peels, which are often burned, discarded, or landfilled, leading to environmental pollution, greenhouse gas emissions, and inefficient resource utilization. In this context, biorefining has emerged as a sustainable approach for converting agro-industrial waste into high-value bio-based products. This review focuses on apple pomace and wheat bran as representative and abundant by-products rich in dietary fiber (DF), polyphenols, vitamins, minerals, and other bioactive compounds, with significant potential for food and industrial applications. The scope of this review is to critically evaluate recent advances in the extraction, modification, and application of DF derived from these two sources. Particular emphasis is placed on the integration of advanced technologies, including ultrasound-assisted, microwave-assisted, and supercritical fluid extraction, which enhance fiber recovery efficiency while enabling precise modification of functional properties such as solubility, viscosity, and fermentability. These technological interventions facilitate the effective incorporation of recovered DF into food systems and biodegradable material applications. Key findings indicate that DF from apple pomace and wheat bran can be successfully utilized in the development of fortified foods such as bread, biscuits, cakes, and breakfast cereals, improving their nutritional and functional attributes. Additionally, extracted fiber shows strong potential in the production of biodegradable packaging materials, edible films, and other eco-friendly bioproducts, thereby reducing reliance on petroleum-based plastics. The review further identifies existing challenges, including scalability, process optimization, and standardization, and outlines future research directions focusing on technological innovation, industrial integration, and sustainability assessment. Overall, this study highlights the critical role of agro-waste valorization in advancing a circular bioeconomy, reducing environmental impacts, and supporting sustainable development goals related to health, industry, responsible consumption, and climate action. It also underscores the potential of these approaches to create economic opportunities and promote a resource-efficient, zero-waste future.</p> Graphical Abstract <p></p>