The Kingdom Amoebozoa, which means amoeboid animals, is a large group of living organisms that currently comprises a few thousand species, although undoubtedly most of its species are still to be discovered. They inhabit marine and freshwater environments as well as soils worldwide, and many species are parasites of other organisms.

The group is primarily unicellular and microscopic, although many of its species form macroscopic colonies during sexual reproduction. They are mainly characterized by having amoeboid cells at least in some phases of their life cycle. Amoeboid cells are wall-less, deformable cells that often form filamentous or lobulated extensions to hunt or move on a substrate. Additionally, this group is typical for having mitochondria with branched tubular crests, although in some exceptional groups, mitochondria have disappeared, an extraordinarily rare feature in the Eukaryota Domain. The centre of the cell usually has a granular zone called endoplasm and a peripheral zone with fewer organelles called ectoplasm. During cellular movements, the endoplasm transforms into ectoplasm and vice versa repeatedly, causing displacement. During locomotion, an anterior and a posterior region can be defined, which disappear when the cell is at rest. Most species have naked cells, but some protect themselves with tiny scales or even build shells within which they live and only come out to feed. Some species form resistance cysts in unfavourable conditions. Excluding few exceptions, they lack flagella and do not form structures supported by microtubules except during cell division.

Feeding primarily occurs through phagocytosis, a process by which the cell envelops and incorporates small organic fragments or microorganisms into vacuoles in which they will be digested. However, many species are parasitic on animals. Although they are usually solitary organisms, in some lineages, amoeboid cells group together to form well-defined structures, often a few millimeters in size, which produce resistance cysts called spores.

It is a very ancient kingdom, related to the Animalia and Fungi Kingdoms.