The burden of proof is the obligation to shift the accepted conclusion away from an oppositional opinion to one's own position.

The burden of proof is often associated with the Latin maxim semper necessitas probandi incumbit ei qui agit, the best translation of which seems to be: "the necessity of proof always lies with the person who lays charges." This is a statement of a version of the presumption of innocence that underpins the assessment of evidence in some legal systems, and is not a general statement of when one takes on the burden of proof.