Bacterial plasma membranes, mainly composed of phospholipids and proteins, separate the interior of a cell from their environment and maintain cell homeostasis. Early notions of membrane organization gave rise to a model in which a homogeneous lipid bilayer permits free protein diffusion. However, proteins and phospholipids are distributed unevenly in bacterial membranes, and specific membrane localization is often crucial for protein activity or function. Bacterial membrane domains with different lipid compositions and with differential physical properties in comparison with the surrounding membrane have now been described. These membrane domains appear to influence localization, diffusion, and function of membrane proteins, and thereby seem to be involved in many cellular processes. Here, we describe the different types of bacterial membrane domains and discuss their involvement in various bacterial cellular processes.