We present resonance gradient metasurfaces that enable continuous tuning of high-Q resonances across an ultra-broadband wavelength range. This tunability is achieved by gradually adjusting the geometric parameters of unit cells along one axis of the metasurface. These metasurfaces support broadband biosensing and precisely control vibrational light-matter coupling (Adv. Mater. 2024, 36, e2314279). Additionally, in combination with a tunable infrared laser, they facilitate resonantly enhanced optical harmonic generation over a wide spectral range (Adv. Mater. 2024, 36, e2307494). These advancements offer a versatile platform for next-generation light-generation technologies and advanced biosensing applications.