Lactobacillus Acidophilus is in the kingdom of Bacteria, but more specifically Monera, the only kingdom of prokaryotic organisms. It is in the division Firmicutes, meaning that it produces endospores that can survive extreme conditions, and that is it is gram- positive. It belongs to the Bacilli class, the class of bacteria that contains unharmful bacteria, and is from Lactobacillales, an order of Gram-positive bacteria  that contain all lactic acid bacteria. It is of the genus Lactobacillus, a genus of Gram-positive facultative anaerobic  or microaerophilic bacteria, and is the species L. Acidophilus