Foldable articulated arm comprising a first rod - shaped element, a second rod - shaped element and a third rod - shaped element foldable one on another and at least three stretching elements of said rod - shaped elements, arranged to form a system of four - bar linkages, further comprising a plurality of joint elements of said rod - shaped elements and said stretching elements and having, at the opposite ends, retaining means for a respective combining with a tube and an umbrella sheet, wherein said rod - shaped elements, said joint elements, said stretching elements and said retaining means are all made integral in a single piece of plastic material constituting said foldable articulated arm, wherein from said at least three stretching elements, a first stretching element has one free end and one opposite end hinged to said first rod - shaped element, a second stretching element has one end hinged to said first stretching element and one opposite end hinged to said second rod - shaped element and a third stretching element has one end hinged to said first rod - shaped element and one opposite end hinged to one end of said third rod - shaped element, wherein said third stretching element essentially comprises a flexible ribbon, wherein the arm comprises a runner sliding on the second rod - shaped element, the third stretching element being a flexible ribbon which is constrained to the second rod - shaped element by said runner and wherein the second stretching element is in the shape of a flexible ribbon having one end combined with the back side of the second rod-shaped element and one end with the first stretching element. - shaped element, a second rod - shaped element and a third rod - shaped element foldable one on another and at least three stretching elements of said rod - shaped elements, arranged to form a system of four - bar linkages, further comprising a plurality of joint elements of said rod - shaped elements and said stretching elements and having, at the opposite ends, retaining means for a respective combining with a tube and an umbrella sheet, wherein said rod - shaped elements, said joint elements, said stretching elements and said retaining means are all made integral in a single piece of plastic material constituting said foldable articulated arm, wherein from said at least three stretching elements, a first stretching element has one free end and one opposite end hinged to said first rod - shaped element, a second stretching element has one end hinged to said first stretching element and one opposite end hinged to said second rod - shaped element and a third stretching element has one end hinged to said first rod - shaped element and one opposite end hinged to one end of said third rod - shaped element, wherein said third stretching element essentially comprises a flexible ribbon, wherein the arm comprises a runner sliding on the second rod - shaped element, the third stretching element being a flexible ribbon which is constrained to the second rod - shaped element by said runner and wherein the second stretching element is in the shape of a flexible ribbon having one end combined with the back side of the second rod-shaped element and one end with the first stretching element.