Abstract: A nestable box spring foundation includes support modules each formed of a single length of wire defining a top base, a bottom base, and four straight legs. The top base is welded to a wire grid assembly and includes two upper wire segments each having a straight wire portion and respective first and second curved end portions, each upper wire segment lying in a first plane with the straight wire portions lying in angularly converging mirror image relation to each other, each upper wire segment being spaced from one another with first end portions thereof lying closer together than second end portions thereof. The bottom base includes two straight lower wire segments lying in parallel relation to and in a second plane with one another and a straight cross wire segment fixedly intersecting orthogonally the lower wire segments proximate first ends thereof, with the first plane being parallel with the second plane.