Safety system for a machine tool of the type provided with at least one movable element, said safety system comprising: - a delimitation structure which is provided with an opening for access of an operator; - a first presence detector (F1, R1) which defines, together with said delimitation structure, a first zone which is configured to receive, when in use, said machine tool; - a first voluntary activation device which is placed outside said first zone; - a second presence detector (F2, R2) defining, together with said delimitation structure, a second zone inside said first zone and, together with said delimitation structure and said first presence detector (F1, R1), a third zone which is placed in said first zone between said opening and said second zone; at least one passage being defined between said third zone and said second zone to allow an operator to pass from said third zone to said second zone, and vice versa; - a second voluntary activation device which is placed in said third zone and operatively connected with said first voluntary activation device and said second presence detector (F2, R2); and - a control system to control the movement speed of said at least one movable element, said control system being operatively connected with said first presence detector (F1, R1) and said first voluntary activation device, such that when an operator accesses said third zone while interfering with said first presence detector (F1, R1), said control system orders said at least one movable element to move with a first speed, and such that when said first voluntary activation device is subsequently activated said control system orders said at least one movable element to move with a second speed which is higher than said first speed, and such that when an operator moves from said third zone to said second zone while interfering with said second presence detector (F2, R2), said control system orders said at least one movable element to move with said second speed after activating, sequentially, said second voluntary activation device and said first voluntary activation device. - a delimitation structure which is provided with an opening for access of an operator; - a first presence detector (F1, R1) which defines, together with said delimitation structure, a first zone which is configured to receive, when in use, said machine tool; - a first voluntary activation device which is placed outside said first zone; - a second presence detector (F2, R2) defining, together with said delimitation structure, a second zone inside said first zone and, together with said delimitation structure and said first presence detector (F1, R1), a third zone which is placed in said first zone between said opening and said second zone; at least one passage being defined between said third zone and said second zone to allow an operator to pass from said third zone to said second zone, and vice versa; - a second voluntary activation device which is placed in said third zone and operatively connected with said first voluntary activation device and said second presence detector (F2, R2); and - a control system to control the movement speed of said at least one movable element, said control system being operatively connected with said first presence detector (F1, R1) and said first voluntary activation device,