A criminal accomplice is a person who knowingly, voluntarily, or intentionally assists another person in the commission of a crime—or under some circumstances, a person who fails to prevent another person from committing a crime. Unlike a person who aids and abets a crime by helping with the planning of the crime but is often not present at the scene of the crime—and unlike an accessory after the fact, who is not present at the scene of the crime but assists after the commission of the crime to help the perpetrator avoid arrest or punishment—an accomplice actively participates in the commission of the crime. For example, a person who acts as a lookout or getaway driver for a bank robbery is an accomplice.

In many states the traditional distinctions between the culpability of accomplices and principals to a crime have been replaced by statute—including the felony murder rule that may make an accomplice guilty of first degree or capital murder if he was the lookout or getaway driver for a bank robbery that resulted in a death.

In Hawaii, the concept of a criminal accomplice is addressed under Hawaii Revised Statutes (HRS). According to HRS §702-221, an accomplice is someone who, with the intention of promoting or facilitating the commission of an offense, aids, agrees to aid, or attempts to aid another person in planning or committing the offense. The law does not require the accomplice to be present at the crime scene. Hawaii law also follows the principle of the felony murder rule, as outlined in HRS §707-701.5, which states that if a person is an accomplice to a crime that is a felony and someone dies as a result of the commission of that felony, the accomplice can be charged with murder in the second degree. This applies even if the accomplice's role was as a lookout or getaway driver and they did not directly cause the death. The statutes effectively abolish the traditional distinctions between principals and accomplices, holding all parties involved in the commission of a felony where a death occurs equally culpable for murder.