The genus Aenictus is a diverse group of army ants in the Old World tropics and subtropics. The Southeast Asian species of the Aenictus ceylonicus group are revised to include twenty-three species (4 named and 19 new species): Aenictus appressipilosus sp. n., A. baliensis sp. n., A. brevipodus sp. n., A. concavus sp. n., A. cylindripetiolus sp. n., A. eguchii sp. n., A. formosensis Forel, 1913 stat. n., A. fuchuanensis Zhou, 2001, A. gonioccipus sp. n., A. itoi sp. n., A. jawadwipa sp. n., A. khaoyaiensis sp. n., A. lifuiae Terayama, 1984, A. longicephalus sp. n., A. maneerati sp. n., A. minipetiolus sp. n., A. pilosus sp. n., A. pinkaewi sp. n., A. sundalandensis sp. n., A. thailandianus Terayama & Kubota, 1993, A. watanasiti sp. n., A. wilaiae sp. n., and A. wiwatwitayai sp. n. Aenictus ceylonicus var. formosensis Forel is removed from synonymy with A. ceylonicus and raised to full species. Lectotype and paralectotypes are designated for A. ceylonicus. Redescriptions of Aenictus ceylonicus (Mayr, 1866) (India and Sri Lanka) and A. doryloides Wilson, 1964 (India) are provided. The queen of A. cylindripetiolus is described. A key to the Southeast Asian species of the group is given based on the worker caste. Most of the Southeast Asian species of this species group have more or less limited distribution ranges. This may be due to the poor dispersal ability generally seen among the Aenictus species, in which the propagule (reproductive unit) is an apterous queen plus accompanying workers.