Lester Joseph Gillis (December 6, 1908 – November 27, 1934), also known as George Nelson and Baby Face Nelson, was an American bank robber who became a criminal partner of John Dillinger when he helped Dillinger escape from prison in Crown Point, Indiana. Later, the Federal Bureau of Investigation (FBI) announced that Nelson and the remaining gang of bank robbers were collectively "Public Enemy Number One".
The "Baby Face Nelson" nickname derived from Gillis being a short man with a youthful appearance; however, in the professional realm, Gillis's fellow criminals addressed him as "Jimmy". A violent bank robber, Lester Joseph Gillis has killed more agents of the FBI than any other criminal. FBI agents fatally wounded Baby Face Nelson in The Battle of Barrington (27 November 1934), fought in a suburb of Chicago.