In common law jurisdictions, the doctrine of merger is a legal concept in criminal law. It is invoked when a charged offense is completely subsumed by another offense. To be correctly applied, the offense to be merged must have no different elements from the consuming offense.

Essentially, it prevents a defendant from being convicted of lesser included crimes along with the more serious crime. For example, the doctrine of merger prevents one from being convicted of attempted murder and murder because all of the elements of attempted murder are included in the crime of murder. Similarly, manslaughter cannot act as the "underlying felony" for the purposes of a felony murder charge, since it would have the effect of making all manslaughters felony murder.