Bacillus nealsonii is a species of bacteria first isolated from a spacecraft-assembly facility. Its spores are ó-radiation resistant. It is Gram-positive, facultatively anaerobic, rod-shaped and produces endospores. Its type strain is FO-92<sup>T</sup> (=ATCC BAA-519<sup>T</sup> =DSM 15077<sup>T</sup>).
This species has been recently transferred into the genus Niallia. The correct nomenclature is Niallia nealsonii.