Thallus is an undifferentiated vegetative tissue of some non-mobile organisms.
Thallus may also refer to:
Thallus (historian), the chronologer/historian Thallus (poet), the Roman era Greek epigrammatist
See also Thallium, a toxic element named after the scientific term due to the green color it produces in flame Thali dialect, also known as Thalli, a dialect of Pakistan