A motor vehicle comprising two side panels (12,13) and a split rear backrest, which is arranged between said two side panels (12,13) and comprises: - a first and a second backrest (8,9), which respectively comprise a first and a second lower portion (18,19), arranged side by side along a horizontal axis, and are independently rotatable about said horizontal axis; - a shaft, extending along said horizontal axis and comprising: a) two axially opposite ends, defining respective fastening elements (24,22; 24a,22a), which are respectively coupled to said side panels (12,13), in a rotating manner about said horizontal axis, or are hinged to respective support brackets fixed to said side panels or to a floor of the motor vehicle; b) a first segment arranged within said first lower portion; c) a second segment, fixed with respect to said first segment, axially protruding from said first lower portion and rotationally engaging an axial seat formed in said second lower portion; - two coupling elements (28, 29) respectively carried by said first and second backrests (8, 9) and releasably fixed to said side panels (12, 13); said fastening elements (24,22; 24a,22a) and said coupling elements (28, 29) defining the only four fastening points to engage said backrests (8, 9) in said motor vehicle; characterized in that said first segment is fixed with respect to said first lower portion, and in that it further comprises two pairs of bushings (30a, 30b) coupling said second segment to said second lower portion; each of said pairs of bushings being constituted by: - an inner bushing (31a, 31b), fitted on said second segment in an angularly fixed position; - an outer bushing (32a, 32b), coupled to said second lower portion in an angularly fixed position and fitted on the corresponding inner bushing (31a, 31b) in a rotatable position. - a first and a second backrest (8,9), which respectively comprise a first and a second lower portion (18,19), arranged side by side along a horizontal axis, and are independently rotatable about said horizontal axis; - a shaft, extending along said horizontal axis and comprising: a) two axially opposite ends, defining respective fastening elements (24,22; 24a,22a), which are respectively coupled to said side panels (12,13), in a rotating manner about said horizontal axis, or are hinged to respective support brackets fixed to said side panels or to a floor of the motor vehicle; b) a first segment arranged within said first lower portion; c) a second segment, fixed with respect to said first segment, axially protruding from said first lower portion and rotationally engaging an axial seat formed in said second lower portion; a) two axially opposite ends, defining respective fastening elements (24,22; 24a,22a), which are respectively coupled to said side panels (12,13), in a rotating manner about said horizontal axis, or are hinged to respective support brackets fixed to said side panels or to a floor of the motor vehicle; b) a first segment arranged within said first lower portion; c) a second segment, fixed with respect to said first segment, axially protruding from said first lower portion and rotationally engaging an axial seat formed in said second lower portion; - two coupling elements (28, 29) respectively carried by said first and second backrests (8, 9) and releasably fixed to said side panels (12, 13); said fastening elements (24,22; 24a,22a) and said coupling elements (28, 29) defining the only four fastening points to engage said backrests (8, 9) in said motor vehicle; characterized in that said first segment is fixed with respect to said first lower portion, and in that it further comprises two pairs of bushings (30a, 30b) coupling said second segment to said second lower portion; each of said pairs of bushings being constituted by: - an inner bushing (31a, 31b), fitted on said second segment in an angularly fixed position; - an outer bushing (32a, 32b), coupled to said second lower portion in an angularly fixed position and fitted on the corresponding inner bushing (31a, 31b) in a rotatable position. - an inner bushing (31a, 31b), fitted on said second segment in an angularly fixed position; - an outer bushing (32a, 32b), coupled to said second lower portion in an angularly fixed position and fitted on the corresponding inner bushing (31a, 31b) in a rotatable position.