The Jaw muscle is the strongest muscle. Not the tongue. Even Wikipedia has doubts about this one:

"The statement that "the tongue is the strongest muscle in the body" appears frequently in lists of surprising facts, but it is difficult to find any definition of "strength" that would make this statement true. Note that the tongue consists of eight muscles, not one."

Thank you, someone had to say it.

You forgot to add 'for its size'. it can generate the most force per lb of muscle mass, but for actual physical strength neither is the strongest muscle in the body.