The thalloyphytes is a polyphyletic group of non-mobile organisms traditionally described as "relatively simple plants" or "lower plants" with undifferentiated bodies (thalli). They were a defunct division of Kingdom Plantae, the Thallophyta (or Thallobionta) that included fungus and algae, and sometimes lichens, mosses, and liverworts, occasionally bacteria and the Myxomycophyta.

They are sometimes referred to as "thalloid plants", as opposed to vascular plants. Stephan Ladislaus Endlicher, a 19th-century Austrian botanist, separated the Vegetable Kingdom (equivalent of Kingdom Plantae) into the Thallophytes and the Cormophytes (vascular plants) in 1836. Thallophytes were known as the Thallogens according to John Lindley, an English botanist in the 19th century. Likewise, Cormophytes were also known as Cormogens in the Lindley system.