A plain bearing, or more commonly sliding bearing and slide bearing (in railroading sometimes called a solid bearing, journal bearing, or friction bearing[citation needed]), is the simplest type of bearing, comprising just a bearing surface and no rolling elements. Therefore, the journal (i.e., the part of the shaft in contact with the bearing) slides over the bearing surface. The simplest example of a plain bearing is a shaft rotating in a hole. A simple linear bearing can be a pair of flat surfaces designed to allow motion; e.g., a drawer and the slides it rests on[1] or the ways on the bed of a lathe.

Plain bearings, in general, are the least expensive type of bearing. They are also compact and lightweight, and they have a high load-carrying capacity.

Plain bearing construction may be solid or with a split joint (wrapped bearings) for easier installation. It is important to match the bearing to the application. High loads call for bearings with increased contact area and high load bearing capacity. Bearings with solid lubricants are designed to operate at higher temperatures than those lubricated with oil or grease. And high speed applications call for special lubricants to minimize heat build-up and friction.

Plain bearings are manufactured with different constructions and product selection depends on the operating conditions of the application and performance requirements.