Nitrospira inopinata is a bacterium from the phylum Nitrospirota.

This phylum contains nitrite-oxidizing bacteria playing role in nitrification.

However N. inopinata was shown to perform complete ammonia oxidation to nitrate thus being the first comammox bacterium to be discovered.

Initial inoculum was obtained in 2011 from microbial biofilm growing on metal surface of the pipe covered by hot water (56 °C, pH 7.5), which was raised from 1 200m deep oil exploration well.

[3] Genome of N. inopinata was released in 2015 represented by 3.3 Mbp, with 3 116 genes and 59.2% GC content.