<p>During the slaughter process of livestock and poultry, a substantial quantity of by-products are generated, which are usually discarded and remain underutilized. However, with in-depth research of livestock and poultry by-products by global scholars, it has been discovered that livestock and poultry slaughter by-products are rich in bioactive proteins. Among these, collagen stands out as an important biological macromolecule with significant nutritional value and bioactivity. In recent years, the characterization, development, and utilization of collagen from livestock and poultry by-products have become a hot topic among scholars worldwide. Therefore, this paper reviews the sources, extraction methods, structures and bioactivities of collagen in livestock and poultry slaughter by-products, and introduces the progress of collagen application in the field of food; it also looks forward to the future research direction of collagen in livestock and poultry slaughter by-products. It aims to provide new ideas for the high-value utilization of collagen in livestock and poultry slaughter by-products.</p>