William "Bunk" Moreland is a fictional character in The Wire, played by Wendell Pierce. Bunk's character is based on a retired Baltimore detective named Oscar "The Bunk" Requer. He is portrayed as a generally competent, if profane and curmudgeonly detective. Like his best friend Jimmy McNulty, he also has problems related to infidelity and alcohol abuse, although he is more mindful than McNulty of the department's chain of command.

According to series creator David Simon, Pierce was cast immediately after completing his audition for the part. In Jonathan Abrams' book All the Pieces Matter, about the process of making The Wire, Simon described Pierce's state of mind at the audition: "He was really pissed off. He had gotten in an argument with a cab driver. It was one of those sort of trying-to-hail-a-cab-while-black moments in New York, and he came in and he was steaming."

Although he tried to apologize for being upset, the casting staff felt his attitude was perfect for a stressed-out Baltimore homicide detective. Pierce was not aware of the rationale until much later. He described feeling somewhat indignant upon learning about it, but told Abrams, "The fact that I would bring it up in the middle of a major audition shows some gumption on my part."

Lance Reddick, who was later cast as Cedric Daniels, was originally called in to audition for Moreland.

Bunk attended Edmondson High School in West Baltimore, where he played lacrosse well enough to make the all-city team. He lives in Randallstown, a predominantly African-American suburb, with his wife Nadine and three children. Bunk worked as a patrolman in Baltimore's Southwestern District before becoming a homicide detective. He is a frequent cigar smoker, and habitual drinker.

Bunk serves as Jimmy McNulty's lone ally in the Baltimore Police Department's Homicide Unit, informing him of its happenings while chiding him for getting involved in the Barksdale case. He is also the primary investigator for the murder of William Gant, who testified against D'Angelo Barksdale. Omar Little informs Bunk that the shooter is a Barksdale soldier called Bird and agrees to testify against Bird in court. Because of this, Bunk persuades his colleague Ray Cole not to arrest Omar for the murder of Stinkum, a Barksdale associate.

When Omar is at the police station, Bunk discovers they attended the same high school, beginning an ongoing association between the two. At Sergeant Jay Landsman's insistence, Bunk and McNulty review the Deirdre Kresson murder, which ultimately turns out to be related to the Barksdales and is solved as part of the final arrests of D'Angelo and Wee-Bey Brice.

With McNulty having been bumped out to the Marine Unit, Bunk is partnered with Lester Freamon, and they are quickly recognized as the most efficient detectives in Homicide. Landsman assigns them to investigate the deaths of fourteen Jane Does in a shipping container at the Port of Baltimore. They are detailed with Officer Beadie Russell from the Port Authority, who initially found the bodies. Bunk and Freamon track down the ship which carried the container and holds it in port in Philadelphia to question the crew.