芽孢杆菌属（Bacillus）属于革兰氏阳性菌，包括模式生物枯草芽孢杆菌和著名的致病菌炭疽杆菌等。此属细菌中有专性需氧菌或兼性厌氧菌，他们遍布于各种环境，有些独立存在亦有些会寄生于其他生物。在不适合生存的情况下，此属细菌可以转化为内生孢子以进入休眠状态，此休眠状态可以持续很久。

在芽孢杆菌属中，其中枯草杆菌可以作为科学研究用的模式生物，还有可致病的炭疽杆菌和蜡样芽孢杆菌。

Bacillus is a genus of gram-positive, rod-shaped (bacillus) bacteria and a member of the phylum Firmicutes. Bacillus species can be obligate aerobes (oxygen reliant), or facultative anaerobes (having the ability to be aerobic or anaerobic). They will test positive for the enzyme catalase when there has been oxygen used or present. Ubiquitous in nature, Bacillus includes both free-living (nonparasitic) and parasitic pathogenic species. Under stressful environmental conditions, the bacteria can produce oval endospores that are not true 'spores', but to which the bacteria can reduce themselves and remain in a dormant state for very long periods. These characteristics originally defined the genus, but not all such species are closely related, and many have been moved to other genera of the Firmicutes.