Abstract: Thermal protector for electric motors, includes: a body which supports all the components of the device, a switch having a fixed part and a mobile part, an element made of bimetallic material, inserted between the mobile part and heating elements designed to heat the bimetallic element, and control the movement of the mobile part away from fixed part, terminals which connect the device to the mains power supply, a terminal which connects the device to the motor power supply connector, wherein the elements include a spiral resistor wound about a straight axis, through which the current supplying the motor passes. The resistor is housed in a seating made in the body, such that its axis is aligned with contact zones of the switch; the seating being cradle-shaped, with a section having a semicircular contour for housing the heating elements, and two smooth side walls, which slant divergently upwards.