Abstract: A breakaway support structure for a sign, light, or mailbox. A foundation post is anchored in the ground and has a projection extending from an upper end. A support post has a sleeve on a lower end which receives the projection. The sleeve and projection are interconnected by at least one linking member which has a preferentially breakable portion. The linking member in one embodiment may be an eyebolt which receives a shear pin. In another embodiment, the projection is a coil spring which is secured on one end to the foundation post and is connected to an annular housing on the lower end of the support post by two spaced fasteners having preferentially breakable portions. In another embodiment, a conventional sign post is retained in a cup-shaped housing that is connected to the projection of the foundation post by at least one linking member which has a preferentially breakable portion.