Life Cycle Assessment (LCA) is a standardized methodology employed to quantify the environmental impacts associated with products and processes throughout their entire life cycle. In the context of biorefineries, facilities that convert biomass into biofuels, bio-based chemicals, and materials, LCA serves as an essential tool to evaluate sustainability trade-offs and guide environmentally sound decision-making. This chapter provides a comprehensive overview of the historical development and methodological foundations of LCA, with particular emphasis on its application in the biorefinery sector. Key methodological elements, including system boundaries, functional units, impact assessment models, and allocation strategies, are discussed in detail. Additionally, the chapter explores contemporary challenges such as data quality, multifunctionality, and regional differentiation, as well as the integration of emerging technologies including artificial intelligence and blockchain to enhance LCA accuracy and transparency. By critically assessing the role of LCA in biorefinery development, this work underscores its relevance for advancing sustainable innovation and policy formulation within the bioeconomy.