源真核生物界(Archezoa)，也称作古真核生物界，是汤玛斯·卡弗利尔-史密斯提出的一个界，包括了粒线体出现以前的真核生物的所有后代物种. 源真核生物曾被认为还没有获得线粒体和典型的高尔基体，核糖体仍与原核生物相似是70S型，是当时所认为的最原始的真核生物类群。这一概念包括了pelobionts与entamoebids (现在属于原阿米巴), 锐滴虫(metamonad), 微孢子虫等. 这一类群在真核生物的rRNA进化树上位于底部. 但是，现在已知这个类群的所有物种都是从具有线粒体的祖先进化而来。基于其它基因的进化树不支持这一类群处于底部的观点。因此，源真核生物界这一概念被废弃了。

Archezoa was a kingdom proposed by Thomas Cavalier-Smith for eukaryotes that diverged before the origin of mitochondria. At various times, the pelobionts and entamoebids (now Archamoebae), the metamonads, and the Microsporidia were included here. These groups appear near the base of eukaryotic evolution on rRNA trees. However, all these groups are now known to have developed from mitochondriate ancestors, and trees based on other genes do not support their basal placement. The kingdom Archezoa has therefore been abandoned.