The Post-Apocalyptic Western and the Dystopian Western share a similar theme in that they both depict bleak futures for civilization. Post-Apocalyptic Westerns occur after a cataclysmic event that leaves the remnants of civilization scattered. This subgenre uses this to revert the world back to a harsh, inhospitable, lawless wasteland that is akin to the Old West. Dystopian Westerns take place in a future society that can be devolved in any number of ways (tyrannical rule, drastic environmental changes, economic collapse, etc.). Dystopian Westerns may incorporate an urban setting and cross into becoming an Urban Western, as well.
George Miller's Mad Max film series takes a considerable amount of inspiration from the Western genre. The series follows a lone wanderer who roams the lawless wasteland of a post-apocalyptic Australia. His travels lead him to settlements fraught with troubles and he, reluctantly, offers them the salvation they're looking for. Although he prefers his trusty "Pursuit Special," Max is adept with almost every form of travel in the wasteland. Throughout the series, he is painted as a cross between Schaefer's Shane and Eastwood's character in Leone's Dollars Trilogy. Miller himself has likened the series, its' setting, and protagonist to the Old American West and classic Western narratives.
The video game Fallout: New Vegas is released as a spin-off to the post-apocalyptic Fallout series. It was released to mostly positive reviews and has, since, been considered a high point in the series. The game's narrative takes places in the Mojave Desert and Las Vegas of a post-nuclear war America. The many different characters and factions in the game reflect stock characters of Westerns. Natives and foreign settlers fight and quarrel over land. Those living in the wasteland are being forced into a new way of life considered to be "modern" compared to their "antiquated" way of living.
Waterworld
In the future. When the polar ice caps melt, the Earth becomes engulfed by water. Drifters sail across the waters of the world on their man-made ships, trading for supplies and salvaging what is left of civilization. Communities of survivors lives in towns called 'Atolls.' Evil pirates known as 'The Smokers' travel across Waterworld in search of a mythical island called 'Dryland.' The Mariner is a mysterious drifter who arrives at an Atoll. He is sentenced to death when the community discover he is a mutant. Led by their evil leader, Deacon, The Smokers attack an Atoll. A woman named Helen and her adopted daughter Enola bribes The Mariner to take them to Dryland. The Mariner, Helen and Enola are pursued by Deacon and the Smokers, when The Mariner learns the tattoo on Enola's back is in reality a map that will lead them to Dryland.