The chapter discusses the AmpC β-lactamases, a class of enzymes that hydrolyze β-lactam antibiotics, primarily penicillins and cephalosporins. Initially identified in *Escherichia coli*, AmpC β-lactamases have since been found in various bacteria, including *Enterobacteriaceae*, *Pseudomonas*, and *Acinetobacter*. These enzymes are typically induced by β-lactam exposure and can be highly expressed in response to such exposure, leading to resistance to a broad spectrum of β-lactams. The chapter details the genetic and regulatory mechanisms that control AmpC expression, including the role of the *ampR* gene and the *ampD* gene in regulation. It also highlights the importance of porin channels and efflux pumps in determining the resistance spectrum of AmpC-producing bacteria. The chapter further discusses the evolution of AmpC enzymes, the detection methods for AmpC β-lactamases, and the clinical relevance of AmpC-producing organisms, emphasizing the challenges in treating infections caused by these bacteria. Finally, it reviews the treatment options for AmpC-producing organisms, noting that carbapenems are generally effective but can lead to carbapenem resistance in some cases.The chapter discusses the AmpC β-lactamases, a class of enzymes that hydrolyze β-lactam antibiotics, primarily penicillins and cephalosporins. Initially identified in *Escherichia coli*, AmpC β-lactamases have since been found in various bacteria, including *Enterobacteriaceae*, *Pseudomonas*, and *Acinetobacter*. These enzymes are typically induced by β-lactam exposure and can be highly expressed in response to such exposure, leading to resistance to a broad spectrum of β-lactams. The chapter details the genetic and regulatory mechanisms that control AmpC expression, including the role of the *ampR* gene and the *ampD* gene in regulation. It also highlights the importance of porin channels and efflux pumps in determining the resistance spectrum of AmpC-producing bacteria. The chapter further discusses the evolution of AmpC enzymes, the detection methods for AmpC β-lactamases, and the clinical relevance of AmpC-producing organisms, emphasizing the challenges in treating infections caused by these bacteria. Finally, it reviews the treatment options for AmpC-producing organisms, noting that carbapenems are generally effective but can lead to carbapenem resistance in some cases.