A safety valve for extraction wells, configured to be installed on a well head and to enclose a tubular material portion inserted inside the well. The tubular material is internally hollow to contain and transport substances extracted from the well. The safety valve includes: a central hole through which the tubular material passes; a blocking system configured to keep the tubular material to be cut fixed with respect to the safety valve; a cutting and closing group configured to cut and close the well under certain operative conditions; and a sealing mechanism configured to effect watertight closing of the well, after the cutting. The cutting and closing group includes a hole saw housed in a respective chamber of the cutting and closing group, rotated by a motorized actuator, and configured to move in a controlled mode along a substantially orthogonal direction with respect to a development direction of the well.