The invention relates to an item of seating furniture (2), in particular an office chair, with a substantially curved supporting shell (14) which has two raised, curved, flexible curved arms (24) and a rigid central piece (16) arranged between said curved arms. Furthermore, the item of seating furniture (2) comprises a covering (30) which is clamped in the manner of a secant between the curved arms (24) of the supporting shell (14), wherein, when the covering (30) is loaded, at least one curved arm (24) is at least partially increasingly raised and/or is at least partially curved in the direction of the central piece (16).