Abstract: An electric spot welding head for a multi-axis industrial robot that has a compact configuration, particularly in a longitudinal direction that goes from the end of the head for the attachment to the robot wrist towards the welding electrodes. This result is achieved primarily by the fact that the electrical transformer mounted on the head has its output connected to the electrode-holding arms arranged, respectively, on a front wall of the body of the transformer and on an end wall of the body of the transformer, for the connection to the electrode-holding arms of the head. The structure of the welding head is completely covered by a casing having a rear opening for connection to the robot wrist and a front opening from which the electrode arms of the welding head protrude.