In microbiology, the minimum inhibitory concentration (MIC) is the lowest concentration of a chemical, usually a drug, which prevents visible growth of a bacterium or bacteria. MIC depends on the microorganism, the affected human being (in vivo only), and the antibiotic itself. It is often expressed in micrograms per milliliter (μg/mL) or milligrams per liter (mg/L).

The MIC is determined by preparing of the chemical in vitro at increasing concentrations, incubating the solutions with separate batches of cultured bacteria, and measuring the results using agar dilution or broth microdilution. Results have been graded into susceptible (often called sensitive), increased exposure, or resistant to a particular antimicrobial by using a breakpoint. Breakpoints are agreed upon values, published in guidelines of a reference body, such as the U.S. Clinical and Laboratory Standards Institute (CLSI), the British Society for Antimicrobial Chemotherapy (BSAC) or the European Committee on Antimicrobial Susceptibility Testing (EUCAST). There have been major discrepancies between the breakpoints from various European countries over the years, and between those from the European Committee on Antimicrobial Susceptibility Testing (EUCAST) and the US Clinical and Laboratory Standards Institute (CLSI).

While MIC is the lowest concentration of an antibacterial agent necessary to inhibit visible growth, minimum bactericidal concentration (MBC) is the minimum concentration of an antibacterial agent that results in bacterial death. The closer the MIC is to the MBC, the more bactericidal the compound.

The first step in drug discovery is often the screening of a library drug candidate for MICs against bacteria of interest. As such, MICs are usually the starting point for larger pre-clinical evaluations of novel antimicrobial agents. The purpose of measuring the minimum inhibitory concentration is to ensure that antibiotics are chosen efficiently to increase the success of treatment.