Aceria waltheri, possible synonym Cymoptus waltheri, is a species of broom mite, affecting Nothofagus menziesii trees. It is sometimes called Beech Witches Broom Mite.
The taxonomic status of the species was unclear, , with sources treating Cymoptus waltheri as either a synonym of Aceria waltheri, or as an accepted species.
Aceria waltheri is a very small mite that makes a tan broom on silver beech trees.
It is native to New Zealand.