A collapsible cardboard concrete form is disclosed. In a particular embodiment the form includes a cardboard box beam having a depressed longitudinal section along an outer portion of its length for added structural integrity. A lateral notch is disposed in the outer portion of the form at intervals and across a width of the form to divide the form into what will be the sides of the form when assembled. The lateral notches include a flexible planar connector of an inner portion of the form to allow the notch to act as a hinge and bend to create each corner of the form. A tab extends from one end of the form and is used to tuck in an opposing end of the form. The surfaces of the form may be coated with wax, or other sealant, to prevent moisture damage to the form as the concrete is curing.