A chair comprising: - a frame having a front transverse element defining a first hinging axis and a rear transverse element defining a second hinging axis, wherein the second hinging axis is situated further back in relation to the first hinging axis and at a greater height than the first hinging axis; - a seat having a front section and a rear section, wherein the front section of the seat is hinged with the frame about said first hinging axis; - a backrest including a backrest panel fixed to a backrest support, wherein the backrest is hinged with the frame about said second hinging axis, wherein the backrest support has a bottom transverse element defining a third hinging axis situated at a lower height than said second hinging axis, wherein said backrest support is hinged with said rear section of the seat about said third hinging axis; wherein the backrest pivots about said second hinging axis between a rest position and a backwards inclined position and wherein in said rest position the distance between the first hinging axis and the second hinging axis has a first value and in said backwards inclined position the distance between the first hinging axis and the second hinging axis has a second value greater than said first value and wherein the frame is deformable elastically so as to allow the variation of the distance between the first hinging axis and the second hinging axis between said first value and said second value; wherein the backrest support has a general U shape and includes two uprights parallel to each other and fixed inside respective seats of the backrest panel, said uprights having respective bottom ends joined together by said bottom transverse element; and wherein said bottom transverse element of said backrest support has two straight side sections aligned with each other along a transverse line defining said third hinging axis and connected together by a curved central section. - a frame having a front transverse element defining a first hinging axis and a rear transverse element defining a second hinging axis, wherein the second hinging axis is situated further back in relation to the first hinging axis and at a greater height than the first hinging axis; - a seat having a front section and a rear section, wherein the front section of the seat is hinged with the frame about said first hinging axis; - a backrest including a backrest panel fixed to a backrest support, wherein the backrest is hinged with the frame about said second hinging axis, wherein the backrest support has a bottom transverse element defining a third hinging axis situated at a lower height than said second hinging axis, wherein said backrest support is hinged with said rear section of the seat about said third hinging axis; wherein the backrest pivots about said second hinging axis between a rest position and a backwards inclined position and wherein in said rest position the distance between the first hinging axis and the second hinging axis has a first value and in said backwards inclined position the distance between the first hinging axis and the second hinging axis has a second value greater than said first value and wherein the frame is deformable elastically so as to allow the variation of the distance between the first hinging axis and the second hinging axis between said first value and said second value; wherein the backrest support has a general U shape and includes two uprights parallel to each other and fixed inside respective seats of the backrest panel, said uprights having respective bottom ends joined together by said bottom transverse element; and wherein said bottom transverse element of said backrest support has two straight side sections aligned with each other along a transverse line defining said third hinging axis and connected together by a curved central section.