<p>Waste Foundry Sand (WFS) is a byproduct from the cast metal sector. It is generated in volumes exceeding 100 million tons each year. As high-quality silica sand, it has potential for recycling in concrete as a replacement for fine aggregates. This helps address the growing issue of foundry waste and reduces the excessive mining of natural aggregates for concrete. This approach supports the United Nations Sustainable Development Goals. While it is widely known that substituting some fine aggregate with WFS in concrete is possible and often beneficial, the variations in properties of WFS concrete are not well-documented or categorized. This review offers a comprehensive and detailed evaluation of WFS's typical effects on concrete performance. It highlights differences in properties and modern optimization techniques. The review also examines less-researched areas, such as WFS processing and its combination with additional cement materials. This aims to create a concrete foundation for optimizing WFS concrete through focused research and effect combination. Current research regarding the long-term durability and life-cycle assessments of concrete made with waste foundry sand reveals significant deficiencies. This review serves as a groundbreaking synthesis of the unexploited potential of waste foundry sand in concrete, carefully addressing essential gaps in long-term durability, life-cycle evaluations, and the 3R principles: Reduce (minimizing the depletion of natural aggregates and lowering embodied carbon), Reuse (redirecting industrial foundry byproducts from landfills to valuable uses), and Recycle (enhancing particle grading for better integration of fines), to provide a detailed pathway for sustainable, resilient, and economically sound construction practices. This review highlights these shortcomings and outlines a definitive direction for future research efforts.</p>