Ladder comprising: - a first and a second fixed handrail (2a, 2b) each of which has an elongated body extending between a lower end and an upper end (3a, 3b), - a pre-set number of rungs transversely engaged to the first and to the second fixed handrail (2a, 2b), - at least one extensible handrail engaged to the elongated body of the first fixed handrail, wherein the extensible handrail is configured to be positioned relative to the first fixed handrail at least between: - a first operative condition in which the extensible handrail is movable along at least one portion of the elongated body of the first fixed handrail, and - a second operative condition in which the extensible handrail is configured to interfere with at least one rung which limits or hinders the mobility thereof along the elongated body of the first fixed handrail, wherein the extensible handrail has at least one first constraint element slidably engaged to the elongated body of the first fixed handrail, characterized in that said at least one first constraint element has: - a main body transversely engaged to the extensible handrail, - a first and a second arm (7a, 7b) projecting as an extension of the main body, distinct and spaced from each other; wherein an intermediate space is defined between respective ends of the first and of the second arm (7a, 7b) opposite the main body; and wherein the first and the second arm (7a, 7b) of the first constraint element define a seat configured to at least partially house the elongated body of the first fixed handrail. - a first and a second fixed handrail (2a, 2b) each of which has an elongated body extending between a lower end and an upper end (3a, 3b), - a pre-set number of rungs transversely engaged to the first and to the second fixed handrail (2a, 2b), - at least one extensible handrail engaged to the elongated body of the first fixed handrail, wherein the extensible handrail is configured to be positioned relative to the first fixed handrail at least between: - a first operative condition in which the extensible handrail is movable along at least one portion of the elongated body of the first fixed handrail, and - a second operative condition in which the extensible handrail is configured to interfere with at least one rung which limits or hinders the mobility thereof along the elongated body of the first fixed handrail, - a first operative condition in which the extensible handrail is movable along at least one portion of the elongated body of the first fixed handrail, and - a second operative condition in which the extensible handrail is configured to interfere with at least one rung which limits or hinders the mobility thereof along the elongated body of the first fixed handrail, wherein the extensible handrail has at least one first constraint element slidably engaged to the elongated body of the first fixed handrail, characterized in that said at least one first constraint element has: - a main body transversely engaged to the extensible handrail, - a first and a second arm (7a, 7b) projecting as an extension of the main body, distinct and spaced from each other; - a main body transversely engaged to the extensible handrail, - a first and a second arm (7a, 7b) projecting as an extension of the main body, distinct and spaced from each other; wherein an intermediate space is defined between respective ends of the first and of the second arm (7a, 7b) opposite the main body; and wherein the first and the second arm (7a, 7b) of the first constraint element define a seat configured to at least partially house the elongated body of the first fixed handrail.