Nanofiltration is a form of filtration that uses membranes to preferentially separate different fluids or ions.

Nanofiltration is not as fine a filtration process as reverse osmosis, but it also does not require the same energy to perform the separation.

Nanofiltration also uses a membrane that is partially permeable to perform the separation, but the membrane's pores are typically much larger than the membrane pores that are used in reverse osmosis.