Lesbian Cop

A female police officer who is a homosexual.

This trope, of course, can be open to Unfortunate Implications; namely, the idea that certain activities and occupations are 'reserved' for men and that any women who choose to partake in them are automatically more 'masculine' (and thus in turn inclined to homosexuality) than those who don't. There is an element of Truth in Television, as naturally some of the women in these occupations (now that they allow women) are lesbians; but this doesn't equal that all lesbians are in traditionally 'male' occupations or that no straight women are.

See also Lesbian Jock, a trope that exists for similar reasons and has similar pitfalls. The Lesbian Cop may be a Fair Cop.

Examples of Lesbian Cop include:

Anime and Manga

Bleach: Depending on your interpretation of her character, Soi Fon may qualify as this; given her position as head of the Keigun (punishment squad) and her Les Yay obsession with Yoruichi. Mind you, this is more apparent in the anime than it is in the manga, but still...
The sheriff in the second volume of Dogby Walks Alone.

Comic Books

Captain Maggie Sawyer of the Metropolis Special Crimes Unit in Superman comics. Introduced in 1987, her sexual orientation was established less than a year later.
Detective Renee Montoya of the Gotham City Police Department was a Batman supporting character for many years before being outed in Gotham Central.
A Psycho Lesbian cop appears in The Punisher. She first appeared in the Garth Ennis run as Soap's new partner, and later returned (her Psycho Lesbian side was mostly explored in the arc with Elite's son).
Sgt. Jackie "Jack Phantom" Kowalski from Top Ten. In the later Beyond the Farthest Precinct mini-series, she is in a relationship with her partner Panthalassa.
Marv's Probation Officer from Sin City.

Film

Margaret from Slither.
Specter from Onward

Literature

Detective Sergeant Stephanopoulis in the Rivers of London books, described in text as looking like "a woman who fought rottweilers" and "a terrifying lesbian". She's actually a very nice person, and an utter professional in the Old-Fashioned Copper mould.
Kate "Casey" Martinelli, the protagonist of a series of mystery novels by Laurie King.
Kate Delafield, hero of a series of detective novels by Katherine V Forrest beginning with Amateur City.

Live-Action TV

On Law and Order SVU, when Olivia asks a female cop if she'd been having an affair with her (male) partner, the cop looks Olivia up and down and replies,

Kristin: Let me make this very clear, Detective: I'd be much more inclined to have an affair with you.

- Olivia herself is constantly subject to Les Yay speculation by fans (lesbian fans, anyway), usually with a relationship with Alex in mind and much pining for the shorter, butcher haircut and leather jacket of the early seasons. It was probably partly in response to this impression that the show made obvious attempts to make her more feminine as the series went on—longer hair, more makeup, nicer clothes, a more "motherly" attitude toward victims and more references to/depictions of her having a boyfriend.
- She is also Mistaken for Gay by a lesbian activist who cites Liv's job and attitude as indicative of being a lesbian. Later, Hilarity Ensues (and lampshades are hung when Liv asks Elliott if he gets a gay vibe from her and he points out that she doesn't have much luck with guys.
Agent Carrie Rivai in the 2008 Knight Rider remake.
Agent Burke's probie in the first episode of White Collar is implied to be one. It's confirmed when she returns in season 2, she has a girlfriend that she met while working in DC and who moved with her back to New York.

Neal Caffrey: [pouting after finding out] Doesn't the FBI have a policy about that?
Peter Burke: That's the military. We don't ask. We don't care.

Kima Greggs of The Wire.
Third Watch raced ahead of this trope in its first episode. Boscorelli, masculine and Irish was accused of being gay as part of a prank. While driving around after who he thought was the prankster, he complained to his partner and asked what she'd think if people thought she was a lesbian. She answered "I'm a female cop, people assume I'm a lesbian."
On NYPD Blue Medevoy donated sperm to a lesbian cop and her girlfriend so they could have a baby.
DC Jo Masters from The Bill.
Roseanne: Roseanne's sister Jackie was a police officer, but while she wasn't a lesbian in the show, Roseanne reveals in the final episode that the series was a book she was writing based on her family and that her sister actually is a lesbian.
On Lip Service, essentially BBC's answer to The L Word, Sam is a soft butch example of this trope.
Mo Connell from Between the Lines is introduced as a lesbian, although it later turns out, in reverse of the normal pattern, that she's Bi the Way.
Rookie Blue: Starting in season 4, Gail Peck.

Video Games

Officer Jo Slade from Dead Rising, for a Psycho Lesbian.

Web Original

On Three Way the show within a show "Ladycops" played with this trope.

Western Animation

Maggie Sawyer in Superman: The Animated Series has the same sexual orientation as her comicbook counterpart, according to Word of God, although the closest they could get to referencing Maggie being gay on-screen was to have her girlfriend be at her bedside when she was in hospital during the first Darkseid story. She goes unnamed, and their relationship isn't elaborated on, but she's there. She's also present, comforting Maggie, after Dan Turpin dies.