Pedicularis palustris, commonly known as marsh lousewort or red rattle,[2] is a plant species in the family Orobanchaceae.

palustris, which occurs in the west of the range, is a straggly biennial plant with a much-branched, usually erect stem up to 60 cm (24 in) tall.

Each bilaterally symmetrical flower has a short stalk and a large, rounded, toothed calyx.

[4] This species can be distinguished from common lousewort (Pedicularis sylvatica) by having two calyx lobes rather than four, and four small teeth at the tip of the upper lip rather than two.

[1] In the British Isles, it mostly occurs in Scotland, Ireland, Wales, western England and East Anglia.