Flotation is a physical-chemical separation process for fine-grained solids. It is based on the different surface wettability of particles: gas bubbles are easily attached to hydrophobic (water-repellent) surfaces and give the particles buoyancy. The prerequisite is, that the gas used is slightly soluble in water (the gas is therefore hydrophobic). As defined in VDMA Specification 24430, this is a separation process in which water-dispersed or suspended substances are transported to the water surface by means of gas bubbles and are then removed from the surface with a clearing device.

The process is used in mining to separate ores and gangue in aqueous slurry (suspension). Flotation has replaced the traditional desludging in most areas.