Trivialism is the view that all sentences (or propositions) are true. That is to say that truth is a trivial matter.
By extension, trivialism has the consequence that all sentences and their negations are true. Hence, for every proposition, φ, both φ and ¬φ are true. As a result, trivialism implies dialetheism, the view that there are true contradictions.
The term is introduced in Graham Priest's book, Doubt Truth to be a Liar, along with the Law of Non-Triviality.