A waveguide radiating element (10) is described comprising: —an electrically conductive support body (2, 12) inside which a first recess (3) is defined, delimited at the front by a radiating opening (4), and laterally delimited by at least one side wall (5, 6); —at least one electrically conductive impedance matching unit (20) having a portion (21) projecting from said side wall (5, 6) and positioned inside the first recess (3), the projecting portion (21) having a step or ramp-shaped surface. The impedance matching unit (20) comprises an attachment portion (22) adjacent to the projecting portion (21) and inside the electrically conductive body (2) a second recess (13) is defined, adjacent to the first recess (3) and communicating with the first recess (3), inside which the attachment portion (22) of the impedance matching unit (20) is coupled.