Structural steel is a category of steel used as a construction material for making structural steel shapes. A structural steel shape is a profile, formed with a specific cross section and following certain standards for chemical composition and mechanical properties. Structural steel shapes, sizes, composition, strengths, storage practices, etc., are regulated by standards in most industrialized countries.

Structural steel members, such as I-beams, have high second moments of area, which allow them to be very stiff in respect to their cross-sectional area.

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structures in which the members are made of steel and are joined by welding, riveting, or bolting. Because of the high strength of steel, these structures are reliable and require less material than other types of structures. Steel structures are distinguished by the diversity of their shapes and by their architectural expressiveness. Fabrication and installation of steel structures are realized through industrial methods. The main disadvantage of steel structures is susceptibility to corrosion, which requires that protective measures, such as the application of special coatings and paints, be taken periodically, thereby increasing service costs.