William O'Neal (April 9, 1949 – January 15, 1990) was an American FBI informant in Chicago, Illinois, where he infiltrated the local Black Panther Party (BPP).

In 1967, when he was about 18 years old, he was caught by FBI agent Roy Martin Mitchell, who had tracked O'Neal down for stealing a car and driving it across state lines to Michigan.

[1] In 1968 the FBI offered him a deal: in exchange for having his felony charges dropped and receiving a monthly stipend, O'Neal agreed to infiltrate the Panthers as a counterintelligence operative (informant).

[2] The FBI had been conducting their illegal COINTELPRO operation since the mid-1950s, expanding their efforts against communists to include black civil rights activists.

[4] In 1969 Hampton was working on the Rainbow Coalition, an alliance among gangs and minority groups in Chicago, and the FBI and police became increasingly concerned about his activities and growing political power.

[5] The FBI required O'Neal to give them a drawing to show the layout of Hampton's apartment on Monroe Street in the West Side, where the Panthers often gathered, so they could prepare a raid.

He gave details about his impressions and experiences working in the Black Panther Party, his relationship with FBI agent Roy Mitchell, and his feelings about his activities and his role.

"[12] In the early hours of January 15, 1990, after visiting with his uncle Ben Heard, O'Neal ran out of the apartment and into traffic on Interstate 290, where he was hit by a car, and killed; he was 40 years old.

Heard said afterward that O'Neal had "cooperated with the FBI to reduce his own potential jail time, then got in way over his head and was forever tortured by the guilt", and that "he never thought it would come to all this.