Epilobium ciliatum is a species of willowherb known by the common names Fringed Willowherb and American Willowherb. This plant is found in many parts of the world. It is native to much of North America and eastern Asia, and it is an introduced species in much of Eurasia and Australia. It may be found in a great variety of habitats, including disturbed areas and roadsides.

This is a clumping perennial often exceeding one and a half meters in height. It has thickly veined lance-shaped leaves which may be up to 15 centimeters long toward the base of the plant. The foliage, stem, and inflorescence are covered in bristly hairs and glands. The trumpet-shaped flowers have four petals which are so deeply notched they look like four pairs. They are white to light purple or pink with dark veining. The fruit is a narrow, hairy capsule up to 10 centimeters in length, and it may be held on a long stalk.

Three subspecies are recognized as valid:

• Epilobium ciliatum ssp. ciliatum
• Epilobium ciliatum ssp. glandulosum (Lehm.) Hoch & P.H.Raven
• Epilobium ciliatum ssp. watsonii (Barbey) Hoch & P.H.Raven

But it appears that E. ciliatum is actually a cryptic species complex: the Rocky Mountain Willowherb (E. saximontanum) is sometimes included as yet another subspecies, while on the other hand it may well be that the three generally-recognized subspecies each consititute a distinct species. In this case, ssp. watsonii would perhaps use the name E. adenocaulon and at any rate include those populations, while E. glandulosum would include the populations referred to as E. bergianum. The other named populations would remain in E. ciliatum.