According to the Library of Congress, the human body has at least 650 skeletal muscles and as many as 840 depending on what counts as a muscle. Some sources count complex muscles as a single muscle, while others count complex muscles' individual parts as separate muscles, which leads to dissent.
The Library of Congress explains that the number of total muscles in the body is much harder to count as many organs and other tissues are technically considered muscle. For instance, the average human body has billions of smooth muscle fibers that occur at the cellular level. Additionally, humans have many muscular organs, including the heart, the uterine muscles and even the tongue.