Weight training is a common type of strength training for developing the strength and size of skeletal muscles. It uses the force of gravity (in the form of weighted bars, dumbbells or weight stacks) to oppose the force generated by muscle through concentric or eccentric contraction. Weight training uses a variety of specialized equipment to target specific muscle groups and types of movement.

Weight training differs from bodybuilding, weightlifting, power lifting and strongman, which are sports rather than forms of exercise. Weight training, however, is often part of the athlete's training regimen. Strength training is an inclusive term for all types of exercise devoted towards increasing muscular strength and size (as opposed to muscular endurance, associated with aerobic exercise, or flexibility, associated with stretching exercise like yoga or Pilates, though endurance and flexibility can improve as a byproduct of training).

Weight training is one type of strength training and the most common, seen by all but specialists as synonymous with strength training. The difference between weight training and other types of strength training is how the opposition to muscular contraction is generated. Resistance training uses elastic or hydraulic forces to oppose muscular contraction and isometric exercise uses structural or intramuscular forces (e.g. doorways or the body's own muscles).