Electrosurgery is the application of a high-frequency electric current to biological tissue as a means to perform a number of actions on the tissue. These include cutting, coagulation, desiccation, and fulguration. The benefits of electrosurgery include the ability to make precise cuts with limited blood loss. Electrosurgical devices are frequently used during surgical operations helping to prevent blood loss in hospital operating rooms or in outpatient procedures.

In electrosurgical procedures, the tissue is heated by an electric current. Although electrical devices may be used for the cauterization of tissue in some applications, electrosurgery is usually used to refer to a quite different method than electrocautery. The latter uses heat conduction from a probe heated by a direct current (much in the manner of a soldering iron), whereas electrosurgery uses alternating current to directly heat the tissue itself.

Often electrosurgery is mistakenly referred to as diathermy. Unlike Ohmic heating by electric current passing through the conductive tissue in conventional electrosurgery, diathermy means dielectric heating, produced by rotation of molecular dipoles in high frequency alternating electric field. This effect is most widely used in microwave ovens which operate at gigahertz frequencies.

Electrosurgery is commonly used in dermatological, gynecological, cardiac, plastic, ocular, spine, ENT, orthopedic, urological, neuro- and general surgical procedures as well as certain dental procedures

Electrosurgery is performed using an electrosurgical generator (also referred to as power supply or waveform generator) and a handpiece including one or several electrodes, sometimes referred to as an RF Knife. The apparatus when used for coagulation in surgery is still often referred to informally by surgeons as a "Bovie," after the inventor.

In bipolar configuration the voltage is applied to the patient using a pair of similarly-sized electrodes. For example, special forceps, with one tine connected to one pole of the AC generator and the other tine connected to the other pole of the generator. When a piece of tissue is held by the forceps, a high frequency electric current flows from one to the other forceps tine, heating the intervening tissue.

In monopolar configuration the patient is attached to the return electrode, a relatively large metal plate or a flexible metalized plastic pad which is connected to the return electrode of the AC source. The surgeon uses a pointed electrode to make contact with the tissue. The electric current flows from the active electrode, through the body to the return electrode, and then back to the electrosurgical generator.