Leptothrix is a genus of Gram-negative bacteria in the class Betaproteobacteria.

[3] The name is from the Greek leptos thrix (literally 'fine hair').

[1] They occur in standing or slow-flowing, ferruginous, neutral to slightly acidic fresh waters with only low concentrations of organic matter.

The energy metabolism of Leptothrix is strictly aerobic, oxidative, and chemoorganoheterotrophic.

Five species are known: L. ochracea, L. discophora, L. cholodnii, L. lopholea, and L. mobilis.