Spironematellidae (previously known as Spironemidae)[1] is a family of heterotrophic flagellates, in the group Hemimastigophora.

They vary in size and shape from the ellipsoid Hemimastix amphikineta (14 × 7 μm) to the vermiform Spironematella terricola (43 × 3 μm), and are united by the possession of two rows of cilia, called kineties.

[2] Phylogenomic analysis shows that Hemimastigophora are a distinct and ancient lineage of eukaryotic organisms, forming a possible sister clade to the supergroup Diaphoretickes.

[3][4] The classification of Spironematellidae, as of 2022:[1]