Protists (ˈproʊtɨst/) are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in moderntaxonomy. Instead, it is "better regarded as a loose grouping of 30 or 40 disparate phyla with diverse combinations of trophicmodes, mechanisms of motility, cell coverings and life cycles."


The protists do not have much in common besides a relatively simple organization—either they are unicellular, or they aremulticellular without specialized tissues. This simple cellular organization distinguishes the protists from other eukaryotes, such asfungi, animals and plants.