The invention relates to an insole, and to an article of footwear provided with such an insole, with application to the design of shoes wherein an improvement in comfort is sought.The insole includes a principal portion 1 designed to accommodate the pressure of a user's foot, comprising at least one deformable cavity 2, 5 filled with a compressible, fluid-permeable material 3, 6 and provided on the one hand with at least one inlet E1, E2 for fluid intake and on the other hand with at least one outlet S1, S2, S3 for exhausting the fluid. Further, the thickness of the principal portion, in the non-deformed state of the cavity, is substantially constant, with the possible exception of the perimeter of the cavity and/or the possible exception of the inlets and/or outlets.