Jay Landsman is a character on the HBO drama The Wire, a fictionalised version of the real-life Baltimore City police officer Jay Landsman. The fictional character of Landsman is portrayed by actor Delaney Williams.

Landsman's role in the police department is that of a supervisory detective sergeant who rarely participates in real investigative work. Landsman generally acts in the best interests of his subordinates, especially those who give him the necessary clearances (closed cases). As a supervisor, Landsman acts in accordance with the wishes of his superior officers, even though, in some cases, he does not necessarily agree with specific commands.

Examples of this are when he is ordered to have Bunk Moreland find Kenneth Dozerman's missing firearm in Season 3 and when a dead state's witness becomes an electoral issue in Season 4. Throughout the series, he is shown as a commander attempting to strike a balance between loyalty to subordinates and superiors, most often favoring the latter. Landsman has only been called to solve a few murders on his own as a supervisor.

While Landsman is a source of comic relief in the series due to his laziness, girth, overeating, and penchant for nonchalantly reading pornographic magazines while on the job, he is also depicted as quick-witted and relatively cultured by Department standards. He possesses a shrewd understanding of the subtle politics in the chain of command, almost always successfully acting in self-preservation and self-promotion without making many enemies. He states that clearly to McNulty, during the first episode of season 2, by saying it is all about self-preservation and it is too bad that McNulty never learned that.

Overall, under Landsman's supervision, the homicide unit ends up often clearing many of the more challenging "whodunit" homicides occurring in Baltimore city, proving him to be an effective sergeant within the department. However, he can be mildly bullying and tends to derive his good humor from schadenfreude, though he is not generally malicious.

He has the duty of ministering in the informal "detective wakes" held in honor of the deceased at Kavanaugh's, the bar frequented by many in the department, a task he completes with uncharacteristic reverence and emotion. Wakes take place in Season 3 (for Ray Cole), Season 4 (for Raymond Foerster) and Season 5 (for the ostracized, but still-living Jimmy McNulty).

Landsman is a squad sergeant in the homicide division of the Baltimore police department. His commanding officer is originally William Rawls. Landsman's squad consists of Jimmy McNulty, Bunk Moreland, Michael Santangelo, Ray Cole, Ed Norris and Vernon Holley. Landsman finds the misfortune of the cops in his unit a constant source of amusement but is also protective of them at times. He is loyal to Rawls and also doggedly pursues the high case clearance rates that Rawls aims for but is realistic about the capabilities of his detectives.

When McNulty goes around the chain of command and incurs Rawls's wrath by being detailed to another unit Landsman appears unsympathetic. He insists that McNulty's work looking at old homicide cases for the detail be put to his advantage to make up for losing a detective. To this end, he insists that McNulty look into the Deirdre Kresson murder case; McNulty is initially reluctant because the case appears unrelated to the Barksdale case.