Ultrafiltration is a filtration process from the field of membrane technology that can be used to separate macromolecules and small particles from a medium.

The prerequisite for the process is a selective filter membrane and a pressure difference in front of and behind this membrane. This results in a so-called "sieve effect", which is created by a fixed pore size of the membrane. All ingredients that are larger than the membrane pores are retained in this way.