A Grease Fitting is a device used in mechanical systems to feed lubricating grease into bearings. It can be fed by a grease gun or a grease nipple. Grease fittings are often referred to as a Zerk fitting, but they have other names as well.

Traditionally, a Grease Fitting is covered with a cap or a simple plug. It may also be covered with a small cup. A spring-loaded hinged cup is sometimes mounted to the fitting and turned to inject oil or grease. The owner's manual can often list lubrication requirements, and knowing the proper grease fitting size for a particular area can make lubrication more convenient.

Grease fittings are relatively inexpensive and are available in a variety of sizes. They may also be installed on riding lawn mowers. If so, they may be located on the front spindles, front wheels, and steering sector. You can also find grease fittings on your riding lawn mower's front spindles or wheels.

When installing a Grease Fitting, you should always make sure it is installed properly. The proper torque depends on the type of fitting and the materials it is installed on. If the fitting is too tight, it can strip or break the threads of the mating hole.