In spite of the advent of extremely large telescopes in the UV/optical/NIR range, the current generation of 8-10m facilities is likely to remain competitive at ground- UV wavelengths for the foreseeable future. The Cassegrain U-Band E cient Spectrograph (CUBES) has been designed to provide high-e ciency (> 40%) observations in the near UV (305-400 nm requirement, 300-420 nm goal) at a spectral resolving power of R > 20,000, although a lower-resolution, sky-limited mode of R ∼ 7,000 is also planned. CUBES will o er new possibilities in many fields of astrophysics, providing access to key lines of stellar spectra: a tremendous diversity of iron-peak and heavy elements, lighter elements as well as Balmer lines and the Balmer jump. The UV range is also critical in extragalactic studies: the circumgalactic medium of distant galaxies, the contribution of different types of sources to the cosmic UV background, the measurement of H2 and primordial Deuterium in a regime of relatively transparent intergalactic medium, and follow-up of explosive transients. The CUBES project has entered Phase B, dedicated to detailed design and construction. First science operations are planned for 2028.
