VEHICLE LOWER PORTION STRUCTURE

A vehicle lower portion structure includes: a seat cushion (12) that is provided in a cabin and that includes a sitting area in which an occupant sits; a seat base (16) that is provided on a vehicle lower side of the seat cushion (12), with at least part of the seat base (16) being disposed under the sitting area, and that supports the seat cushion (12) from below; and a reinforcement member (32) that is provided between the seat cushion (12) and the seat base, that is supported by an upper surface (16A) of a front portion of the seat base (16), and that extends along a vehicle width direction.