Efflux pumps are a class of transmembrane proteins used to pump toxins, drugs, and other substrates from inside the cell to the outside. They include several families, such as the ABC transporter family, the major facilitator superfamily (MDR), the small multidrug resistance family (SMR), and the resistance-nodulation-division (RND) pumps. These pumps are composed of varying numbers of transmembrane domains and are primarily located on the cell membrane of bacteria, fungi, and human cells. Efflux pumps are involved in toxin exclusion and drug resistance in cells, driving substrate efflux by utilizing ATP hydrolysis or proton gradient. The expression of efflux pumps is tissue- and cell-specific, and mutations or dysregulation of their genes are associated with various diseases, particularly antibiotic resistance and chemotherapy resistance.