A motor vehicle seat, comprising: a one-piece structure forming a seat bottom and a backrest; a height adjustment mechanism operable to adjust and fix the height of the one-piece structure; and a tilting control system, operable for adjusting and fixing the inclination of the structure; characterized in that the height adjustment mechanism is provided with a pair of side brackets (10a, 10b) fixable on two respective opposite sides of the seat, each bracket being fixable to a floor panel of the motor vehicle or movable slides of guides for adjusting the longitudinal position of the seat; each side bracket (10a, 10b) has a plurality of catches for height adjustment, aligned in pairs along a plurality of horizontal geometrical axes located at different heights; provided on two opposite sides of the one-piece structure are two height adjustment elements selectively engageable in one of the pairs of catches for height adjustment of both the side brackets (10a, 10b); wherein the elements for height adjustment comprise a pair of pins projecting from two opposite sides of the one-piece structure in a connection zone between the seat bottom and the backrest, and wherein the catches of height adjustment are through openings, wherein the adjustment catches are either in the form of separate through holes (13', 13", 13'") formed in each side bracket (10a, 10b), or the adjustment catches in each side bracket (10a, 10b) are formed by a single shaped opening which has different interconnecting branches, each of which forms one of said height adjustment catches; and wherein the tilting control system either comprises, on each of two opposite sides of the seat bottom, an articulated leverage, which includes an upper lever articulated to the seat bottom and a lower lever articulated to the upper lever and to a respective bracket (10a, 10b); or wherein the tilting control system comprises: on each of two opposite sides of the seat bottom, a leverage with a lever having a first end pivotally mounted to a respective bracket (10a, 10b) and a second end; a horizontal bar which connects the second ends of the levers, the connecting bar being mounted on the seat bottom of the one-piece structure. a one-piece structure forming a seat bottom and a backrest; a height adjustment mechanism operable to adjust and fix the height of the one-piece structure; and a tilting control system, operable for adjusting and fixing the inclination of the structure; characterized in that the height adjustment mechanism is provided with a pair of side brackets (10a, 10b) fixable on two respective opposite sides of the seat, each bracket being fixable to a floor panel of the motor vehicle or movable slides of guides for adjusting the longitudinal position of the seat; each side bracket (10a, 10b) has a plurality of catches for height adjustment, aligned in pairs along a plurality of horizontal geometrical axes located at different heights; provided on two opposite sides of the one-piece structure are two height adjustment elements selectively engageable in one of the pairs of catches for height adjustment of both the side brackets (10a, 10b); wherein the elements for height adjustment comprise a pair of pins projecting from two opposite sides of the one-piece structure in a connection zone between the seat bottom and the backrest, and wherein the catches of height adjustment are through openings, wherein the adjustment catches are either in the form of separate through holes (13', 13", 13'") formed in each side bracket (10a, 10b), or the adjustment catches in each side bracket (10a, 10b) are formed by a single shaped opening which has different interconnecting branches, each of which forms one of said height adjustment catches; and wherein the tilting control system either comprises, on each of two opposite sides of the seat bottom, an articulated leverage, which includes an upper lever articulated to the seat bottom and a lower lever articulated to the upper lever and to a respective bracket (10a, 10b); or wherein the tilting control system comprises: on each of two opposite sides of the seat bottom, a leverage with a lever having a first end pivotally mounted to a respective bracket (10a, 10b) and a second end; a horizontal bar which connects the second ends of the levers, the connecting bar being mounted on the seat bottom of the one-piece structure. on each of two opposite sides of the seat bottom, a leverage with a lever having a first end pivotally mounted to a respective bracket (10a, 10b) and a second end; a horizontal bar which connects the second ends of the levers, the connecting bar being mounted on the seat bottom of the one-piece structure.