Kelvin is the codename for a GPU microarchitecture developed by Nvidia, and released in 2001, as the successor to Celsius microarchitecture. It was named with reference to William Thomson and used with the GeForce 4 and 3 series.

The GeForce 4 series refers to the fourth generation of Nvidia's GeForce line of graphics processing units (GPUs). There are two different GeForce4 families, the high-performance Ti family, and the budget MX family. The MX family spawned a mostly identical GeForce4 Go (NV17M) family for the laptop market. All three families were announced in early 2002; members within each family were differentiated by core and memory clock speeds. In late 2002, there was an attempt to form a fourth family, also for the laptop market, the only member of it being the GeForce4 4200 Go (NV28M) which was derived from the Ti line.