A child-resistant closure includes a one-piece plastic shell having a base wall with a peripheral edge, an annular skirt, and a bistable snap-action toggle connection between the peripheral edge of the base wall and the skirt such that the skirt is adapted to be moved between two stable positions with respect to the base wall. At least one lug is disposed on the skirt or the base wall for engagement with cooperating structure in a child-resistant mode of operation in a first position of the skirt with respect to the base wall. The skirt is movable with respect to the base wall between the first position and a second positions for selecting between the child-resistant and the non-child-resistant modes of operation of the closure. The bistable snap-action connection preferably includes a continuous annular wall connecting the peripheral edge of the base wall to the skirt, with the annular wall being outwardly conical in one position of the skirt and inwardly conical in the other position of the skirt with respect to the base wall.