David Edgar Herold (June 16, 1842 – July 7, 1865) was an American pharmacist's assistant and accomplice of John Wilkes Booth in the assassination of Abraham Lincoln on April 14, 1865.

The two men then continued their escape through Maryland and into Virginia, and Herold remained with Booth until the authorities cornered them in a barn.

Herold was tried by a military tribunal, sentenced to death for conspiracy, and hanged with three other conspirators at the Washington Arsenal, now known as Fort Lesley J. McNair.

Herold and a group of co-conspirators had originally plotted to kidnap Lincoln, but later decided to kill him, Vice President Andrew Johnson, and Secretary of State William H. Seward in a bid to help the Confederacy's cause.

Another conspirator, George Atzerodt, was supposed to kill Vice President Andrew Johnson, but he got drunk at a bar instead.

They headed to Surrattsville, Maryland (now Clinton), where they picked up weapons that Mary Surratt had left earlier for them at her tavern.

Herold surrendered, but Booth refused to lay down his arms and was shot by Boston Corbett through a crack in the barn wall.

As he had already admitted his involvement in the assassination conspiracy, the only defense his lawyer Frederick Stone could offer was that Herold was feeble-minded[7] and under undue influence from Booth.

In the Afterword, when Vidal explains the extent to which his novel is true to fact, he writes, "As David's life is largely unknown until Booth's conspiracy, I have invented a low-life for him."

David Herold is played by Troy Acree in Season 4, Episode 2 of Unsolved Mysteries which dramatizes the conspiracy theory that Booth escaped capture and died in 1903.