Antibiotic resistance, also known as antimicrobial resistance (AMR), is one of the most serious medical problems facing the world today. After a century in which death from bacterial infection was relatively rare, we now face the possibility of returning to the time of our great-grandparents, in which 50% or more of deaths could be due to bacterial infection. Bioinformatics plays a huge role in studying antibiotic resistance. It can be used to identify antibiotic resistance genes, the origin of resistance genes, the mechanism of antibiotic resistance, and, sometimes, possible alternative treatments. This chapter introduces the concept and mechanisms of antibiotic resistance, which we use as an example of how bioinformatics analyses can be used to solve biological questions.