There is provided a vehicle lower section structure including a rocker that extends in a vehicle front-rear direction at a vehicle width direction outer side, a tunnel section that extends in the vehicle front-rear direction at a central portion in the vehicle width direction, a pair of dash cross members that extend in the vehicle width direction at a lower side of a dash panel, that are separated by the tunnel section, tunnel reinforcement that is disposed at a lower side in the vehicle up-down direction that extends in the vehicle front-rear direction, wherein a first front flange is formed at a front end of the dash cross member in the vehicle front-rear direction, and wherein a second front flange is disposed at a position opposing the first front flange across the dash panel or a floor section.