Peptidoglycan is the major structural component of the bacterial cell wall. It provides resistance against turgor and its cleavage by hydrolases such as lysozymes results in bacteriolysis. Most, if not all, animals produce lysozymes as key effectors of their innate immune system. Recently, highly specific bacterial proteinaceous lysozyme inhibitors against the three major animal lysozyme families have been discovered in bacteria, and these may represent a bacterial answer to animal lysozymes. This paper reviews their properties and phylogenetic distribution, presents their structure and molecular interaction mechanism with lysozyme, discussing their possible biological functions and potential applications.