Abstract: An office chair including a seat portion, a backrest portion joined to the seat portion in an articulated or flexible fashion, and an underframe. The seat portion is articulatingly supported, in an area of a forward edge thereof, on a front bearing pipe and the backrest portion is supported approximately at a hip level through supporting levers on a horizontally extending supporting shaft disposed below the seat portion at a distance therefrom so that solely by shifting one's weight, the inclination of the backrest portion and seat portion can be varied. A locking mechanism, which may be conveniently manipulated from a sitting position and which does not impair the overall appearance of the chair is provided which includes a locking lever disposed in a space between the bearing pipe and the supporting shaft in a housing section of the underframe. The locking mechanism is operable by way of a transmission path from an operating lever arranged in close proximity below the forward edge of the seat portion.