This publication provides a comprehensive and practical overview of duplex stainless steels, focusing on their metallurgy, properties, fabrication, welding practices, corrosion resistance, applications, and quality control requirements. It explains the evolution from first-generation to modern duplex, super duplex, and hyper duplex grades, highlighting their advantages—such as high strength, excellent resistance to chloride stress corrosion cracking, and cost efficiency due to lower nickel content. The guide includes detailed information on microstructures, phase balance, potential detrimental phases, mechanical properties, corrosion behavior, fabrication guidelines, welding considerations, and typical industrial applications across chemical processing, oil & gas, desalination, pulp & paper, and structural engineering.