Ciliate orders

The plagiopylids are a small order of ciliates, including a few forms common in anaerobic habitats.

The peniculids are an order of ciliate protozoa, including the well-known Paramecium and related genera, such as Frontonia, Stokesia, Urocentrum and Lembadion. Most are relatively large, freshwater forms that feed by sweeping smaller organisms into the mouth. They have simple life cycles, and in many cases do not even form resting cysts.

Philasterida (the philasterid ciliates) is an order of ciliates in the subclass Scuticociliatia.

Mobilida is a group of parasitic or symbiotic peritrich ciliates, comprising more than 280 species. Mobilids live on or within a wide variety of aquatic organisms, including fish, amphibians, molluscs, cnidarians, flatworms and other ciliates, attaching to their host organism by means of an aboral adhesive disk. Some mobilid species are pathogens of wild or farmed fish, causing severe and economically damaging diseases such as trichodinosis.

Sessilida is the largest order of the peritrich ciliates.

Pleuronematida is an order of predominantly free-living ciliates in the subclass Scuticociliatia.

thumb|Holotrich, Frontonia leucas, by Schewiakoff, from Gary N. Calkins, The Protozoa 1910 Holotricha was an order of ciliates. The classification has fallen from use as a formal taxon, but the terms "holotrich" and "holotrichous" are still applied descriptively to organisms with cilia of uniform length distributed evenly over the surface of the body.

Urostylida is an order of littoral ciliates. The taxonomy of the order is largely unresolved and still subject to scientific inquiry.