Trimalaconothrus crassipes sp. n. was described for the first time from the roots of the floating aquatic plant, Eichhornia crassipes, River Nile, Girga, Sohag, Egypt. The present species has the characteristic features that are in accordance with those of family Malaconothridae and genus Trimalaconothrus. The present species has specific characters compared with characters of other species of the same genus. These characters are summarized as follows: six dorsal plates, fifteen pairs of notogastral setae, three pairs of granulated rounded organs, three pairs of exobothridial setae (ex1, ex2, ex3), epimeral setal formula (I- IV) is (3-2-2-2) and each coxal epimerae II is characterized by presence of two lateral processes.