The Ultra-High Strength Steels is part of engineering steels courses. The engineering steels is part of the steel applications set of courses. In this courses, the different applications of these steels will be showed. The influence of the Tempering Temperature in the mechanical properties will be presented. After that, the processes used to improve the purity and reduce the inclusion content will be studied. Finally, the maraging steel will be presented. The characteristics of this steel and different applications will be introduced.