John Brown Penington (December 20, 1825 – June 1, 1902) was an American lawyer and politician, from Dover, in Kent County, Delaware.

In 1868, he was appointed United States Attorney for the district of Delaware by President Andrew Johnson and served until 1872.

Penington died at Dover and is buried there in the Old Presbyterian Cemetery, on the grounds of the Delaware State Museum.

It was sent to their home from San Francisco, California, by Cordelia Botkin (an ex-lover of Elizabeth's husband, John Preston Dunning).

The poison was traced back to her, and Penington lived long enough to know the crime would be brought home against the perpetrator.