High intensity focused ultrasound (HIFU, or sometimes MRgFUS for magnetic resonance guided focused ultrasound) is an early stage medical technology that is in various stages of development worldwide to treat a range of disorders.

The fundamental principle is analogous to using a magnifying glass to focus sunlight, generating burning heat. Focused ultrasound uses an acoustic lens to concentrate multiple intersecting beams of ultrasound precisely on a target in the body. Each individual beam passes through tissue with no effect. But at the focal point where the beams converge, the energy can have useful thermal or mechanical effects. The approach may be a stand-alone therapy or utilized to enhance the delivery or effects of chemotherapy or immunotherapy.