TITLE: What is the theorem that has the most proofs?
QUESTION [11 upvotes]: Classical theorems like the irrationality of $\sqrt{2}$ or the infinitude of the primes have lots of proofs. But one theorem in particular, which I studied years ago in an introductory course of Number Theory, called the Quadratic Reciprocity Law, has tons of proofs. Gauss himself provided some of them.
And the question is: Is here a theorem that has more proofs than the Quadratic Reciprocity Law? If you know other theorems that have lots of different proofs, please list below.
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Maybe we can divide the theorems by area.
In Euclidean Geometry, the Pythagorean Theorem won the game.
In Classical Number Theory, the Quadratic Reciprocity Law won the game (I think).
Now, what about Calculus? Algebraic number theory? Real Analysis? Commutative Algebra? Topology? Differential Geometry? Differential Equations? Probability? And so on.

REPLY [3 votes]: Maybe a wrong answer
there are many 'proofs' of the parallel postulate but they all share a problem they are all false