Nabalus altissimus (formerly Prenanthes altissima), commonly called the tall rattlesnakeroot or white lettuce, is a species of plant in the family Asteraceae.

In 2010 it was reclassified from the genus Prenanthes to Nabalus.

[1] This perennial grows in mesic environments including riparian zones and blooms in late summer and autumn.

[2][3] This species occurs in the eastern United States west to Michigan, Missouri, and Texas as well as in Quebec, Canada but is unknown in Mississippi, and Florida.

[2][3] In Texas, it occurs in Jasper and Newton counties in the extreme southeastern part of the state.