In structural engineering, the Structural Steel Joist is a lightweight steel truss consisting, in the standard form, of parallel chords and a triangulated web system, proportioned to span between bearing points.

The main function of Structural Steel Joist is to provide direct support for roof or floor deck and to transfer the load imposed on the deck to the structural frame i.e. beam and column.

In order to accurately design Structural Steel Joist, engineers consider the joist span between bearing points, joist spacing, slope, live loads, dead loads, collateral loads, wind uplift, deflection criteria and maximum joist depth allowed. Many steel joist manufacturers supply load tables in order to allow designers to select the most efficient joist sizes for their projects.