Wikipedia contains a number of articles with mathematical proofs:

Table of contents
1 Theorems of which articles are exclusively devoted to proving them
2 Articles devoted to theorems of which a (sketch of a) proof is given
3 Articles devoted to algorithms of which their correctness is proven
4 Articles where example statements are proven
5 Other articles containing proofs
6 Articles which mention dependencies of theorems
7 Articles giving mathematical proofs within a physical model
8 Other related articles

Theorems of which articles are exclusively devoted to proving them

Articles devoted to theorems of which a (sketch of a) proof is given

Articles devoted to algorithms of which their correctness is proven

Articles where example statements are proven

Other articles containing proofs

Articles which mention dependencies of theorems

Articles giving mathematical proofs within a physical model

Other related articles