A Tension-leg Platform is a vertically moored floating structure normally used for the production of oil or gas, and is particularly suited for water depths greater than 300 metres (about 1000 ft.).

The platform is permanently moored by means of tethers or tendons grouped at each of the structure's corners. A group of tethers is called a tension leg. A feature of the design of the tethers is that they have relatively high axial stiffness (low elasticity), such that virtually all vertical motion of the platform is eliminated. This allows the platform to have the production wellheads on deck (connected direcly to the subsea wells by rigid risers), instead of on the seafloor . This makes for a cheaper well completion and gives better control over the production from the oil or gas reservoir.