We introduce the theory of monoidal Grobner bases, a concept which generalizes the familiar notion in a polynomial ring and allows for a description of Grobner bases of ideals that are stable under the action of a monoid. The main motivation for developing this theory is to prove finiteness results in commutative algebra and applications. A basic theorem of this type is that ideals in infinitely many indeterminates stable under the action of the symmetric group are finitely generated up to symmetry. Using this machinery, we give new streamlined proofs of some classical finiteness theorems in algebraic statistics as well as a proof of the independent set conjecture of Hosten and the second author. (C) 2011 Elsevier Inc. All rights reserved.