Sole with stretchable structure, a footwear article provided with such a sole and its assembly method.The invention relates to a footwear sole where the forepart is associated with a stretchable material making it possible to fit differing foot widths easily; it also relates to the footwear equipped with such a sole and the method for mounting this footwear.It is constituted of a sole base (1) comprising openings (4) in which the lugs (3) of the stretchable part (2) are positioned in a sealed manner.The insole (5) comprises a deformable structure (6) in its forepart. When the wearer's foot is put into a footwear article provided with such a complex, it exerts pressure on the edges of the upper (10) thus causing deformation of the sole. This ability of deforming the sole avoids feelings of compression of the foot.The device according to the invention is intended in particular for the manufacture of footwear with the ability of adapting to differing foot anatomies.