Antimicrobial drugs include those medicines which use antimicrobial agents in the prevention and treatment of infections in humans. An antimicrobial agent is a drug used to prevent and treat the pathogenicity of microorganisms. There are different types of antimicrobial drugs, including antibacterial drugs, antifungal drugs, antiviral agents and antiparasitic drugs. There is increased antimicrobial resistance (AMR) in a variety of human pathogenic microorganisms, which includes Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. The discovery and development of the antimicrobial drugs is aimed at enhancing the pharmacokinetic properties, overcoming pathogen resistance, and extending the spectrum of microorganisms targeted. The five key areas of research in antimicrobial drug discovery are molecular genetics and systems microbiology; synthetic and computational chemistry, and chemoinformatics; high throughput screening (HTS); non-vertebrate model hosts; and light- and nano-based technologies. This book aims to shed light on some of the unexplored aspects of antimicrobial drug discovery. It includes contributions of experts and scientists which will provide innovative insights into this field.