- B
- Baranyai's theorem – Theorem that deals with the decompositions of complete hypergraphs
- Bertrand's ballot theorem – Theorem that gives the probability that an election winner will lead the loser throughout the count
- Bondy's theorem – Bounds the number of elements needed to distinguish the sets in a family of sets
- Bruck–Ryser–Chowla theorem – Nonexistence result for combinatorial block designs
- C
- Corners theorem – Mathematical theorem (arithmetic combinatorics)
- D
- Dilworth's theorem – theorem that the maximum size of an antichain in a finite partial order equals the minimum number of chains into which it can be partitioned
- E
- Erdős–Fuchs theorem – On the number of ways numbers can be represented as sums of elements of an additive basis
- Erdős–Rado theorem – Theorem in combinatorial set theory extending Ramsey's theorem to uncountable sets
- Erdős–Tetali theorem – Existence theorem for economical additive bases of every order
- F
- Folkman's theorem – Theorem in arithmetic combinatorics on finite partitions of the natural numbers
- H
- Hall's marriage theorem – Result in combinatorics and graph theory
- Hockey-stick identity – Recurrence relations of binomial coefficients in Pascal's triangle
- K
- Kneser's theorem (combinatorics) – One of several related theorems regarding the sizes of certain sumsets in abelian groups
- Kruskal–Katona theorem – About the numbers of faces of different dimensions in an abstract simplicial complex
- L
- Labelled enumeration theorem – Counterpart of the Pólya enumeration theorem for the labelled case
- Lagrange inversion theorem – Formula for the Taylor series expansion of the inverse function of an analytic function
- Lindström–Gessel–Viennot lemma – Counts the number of tuples of non-intersecting lattice paths
- M
- MacMahon Master theorem – Result in enumerative combinatorics and linear algebra
- Mirsky's theorem – Characterizes the height of any finite partially ordered set
- Mnëv's universality theorem – Realization of semialgebraic sets by points
- P
- Pólya enumeration theorem – Formula for number of orbits of a group action
- S
- Schur's theorem – One of several theorems in different areas of mathematics
- Stanley's reciprocity theorem – Gives a functional equation satisfied by the generating function of any rational cone
- Szemerédi–Trotter theorem – Bound on the number of incidences between points and lines in the plane
- Szemerédi's theorem – Long dense subsets of the integers contain arbitrarily large arithmetic progressions
