Strength training is the use of resistance to muscular contraction to build the strength, anaerobic endurance and size of skeletal muscles. There are many different methods of strength training, the most common being the use of gravity or elastic/hydraulic forces to oppose muscle contraction. See the resistance training article for information about elastic/hydraulic training, but note that the terms "strength training" and "resistance training" are often used interchangeably.

When properly performed, strength training can provide significant functional benefits and improvement in overall health and well-being including increased bone, muscle, tendon and ligament strength and toughness, improved joint function, reduced potential for injury, increased bone density, a temporary increase in metabolism, improved cardiac function and elevated good cholesterol. Training commonly uses the technique of progressively increasing the force output of the muscle through incremental increases of weight, elastic tension or other resistance, and uses a variety of exercises and types of Category: :Category - :Weight training equipment|equipment to target specific muscle groups. Strength training is primarily an anaerobic activity, although some proponents have adapted it to provide the benefits of aerobic exercise through circuit training.

Strength training differs from bodybuilding, weightlifting, powerlifting and strongman, which are sports rather than forms of exercise. However, participants in these and many other sports often use strength training as part of their training regiment.