Tetrahelia (from Latin tetra- 'four' and helio- 'sun') is a genus of four-ciliated protists belonging to the Endohelea, a group of heterotrophic eukaryotes previously considered heliozoa.

It is a monotypic genus, containing the sole species Tetrahelia pterbica, previously classified as Tetradimorpha.

[1] Tetrahelia are unicellular ciliates with four standard-length centrioles that are shorter than in Heliomorpha and Tetradimorpha, and axopodia generated by a globular centrosome with a distinct granular shell and a microfibrillar core.

There is a thick pseudopellicle layer beneath the cell membrane.

[1] The life cycle of Tetrahelia contains a lazily swimming, purely flagellate stage with fully retracted axopodia.