Muscle & Fitness is an American fitness and bodybuilding magazine founded in 1935 by Canadian entrepreneur Joe Weider. It is published monthly by American Media, Inc.. There is also a companion magazine called Muscle and Fitness Hers, oriented toward women.

Muscle & Fitness has a more mainstream fitness and bodybuilding lifestyle focus than its companion publication, Flex, which mainly covers more specialised "hardcore" and professional bodybuilding topics. It offers many exercise and nutrition tips, while at the same time advertising a variety of nutritional supplements from companies such as Bio-Engineered Supplements & Nutrition.

Many professional bodybuilders are featured in each monthly issue of Muscle & Fitness, such as Gustavo Badell, Darrem Charles, Ronnie Coleman, and Jay Cutler. Figure competitors such as Monica Brant, Jenny Lynn, and Davana Medina are also featured, as are entertainers and other public figures such as Muhammad Ali, Steve Austin, John Cena, 50 Cent,^[2] Jean-Claude Van Damme, Todd Duffee, Triple H, Evander Holyfield, Dwayne Johnson, Brock Lesnar, Nate Marquardt, Stephanie McMahon, Vince McMahon, John Morrison, Mike O'Hearn, Maryse Ouellet, Arnold Schwarzenegger, and Joe Weider himself.

In its December 2015 issue, Muscle & Fitness named Dwayne Johnson its "Man of the Century", crediting him for being "emblematic" of the growth of the fitness industry. Johnson said in the issue, "During the lowest point of my life, this magazine was my rock."^[3]