Abstract: An adjustable quick-release buckle, particularly for masks or similar, of the type provided in combination with a strap (1). The strap has a set of equally spaced teeth (101), projections, transverse ribs, or similar, arranged along the strap (1), and at least on the end portions of said strap (1), covering a predetermined length, and the buckle (2) has removable means (4, 5), preventing the strap (1) from sliding in the loosening direction, and allowing it to slide in the opposite tightening direction, said means (4, 5) being controllable, when the strap (1) is in the disengagement position, also in said loosening direction.