Girls' Night Out Episode

An episode of a show where all the male characters are absent, focusing on the main female characters instead. If the ladies aren't particularly close, such as a Tomboy and Girly Girl dynamic, the circumstances forcing them to work together could lead to mutual respect, and possibly a friendship lasting the rest of the series.

If the genre is action or a superhero, then the plot often involves the heroines having to rescue the heroes, usually with all female villains as well.

A type of A Day in the Limelight. Occasionally a type of Positive Discrimination. Compare The Bechdel Test, which this trope naturally passes.

Examples of Girls' Night Out Episode include:

Anime and Manga

The Excel Saga anime has an all-girl episode called 'Increase Ratings Week'. Although that one is more about invoking Fan Service tropes than anything else.
Tantei Gakuen Q has an episode focusing on Megu, Yukihira and Kuniko upon the latter's arrival to the DDS.
A late episode of Gun X Sword has Wendy, Carmen and Priscilla attempting to infiltrate the Swimsuit Queendom, a Straw Feminist utopia where no men are allowed and everybody has to wear a swimsuit. What do you mean you want to keep your clothes on, Wendy? Are you ashamed of the female body?

Comic Books

An issue of the G.I. Joe Special Missions comic had the female Joes (Scarlett, Lady Jaye, Cover Girl and Jinx) forced to go undercover as cheerleaders at a baseball game. When all the male members are are taken out by mind control, it's up to the girls to save the day.
In a Golden Age Justice Society of America story, the male members of the Justice Society are captured by the villain Brainwave. Wonder Woman (the only female member) recruits the girlfriends (and adopted daughter) of the members who don versions of the male heroes costumes and help rescue them. Particularly odd as the girlfriends were not regular characters in the JSA stories, instead being brought over from the heroes solo series.
Slightly subverted in Stormwatch PHD, when the female cast discover that they have nothing in common.
In a 1989 Uncanny X-Men comic, the female X-men: Storm, Psylocke, Dazzler and Rogue (whose body is taken over by Carol Danver's personality) all teleport for a day of shopping to a Los Angeles mall. Unbeknownst to them a young mutant runaway named Jubilee follows them back through the portal to their hideout in Australia.
Transmetropolitan, twice. The former technically is a Girl's Night In.
A Justice League Task Force story by Peter David featured an (almost) all-female team infiltrating a Lady Land: Wonder Woman, Gypsy, Dolphin, Maxima, Vixen ... and a shapeshifted "J'oann J'onzz".

Live Action TV

Power Rangers RPM had "The Dome Dolls", where the show's female cast went and fought the main villainess of the year after a chemical put all the males in the city to sleep. This is but the most recent example, though. Power Rangers and Super Sentai have girl power focus episodes almost every year at least once.
- Tokusou Sentai Dekaranger had a particularly memorable one, "Twin Cam Angels", which also featured the one and only instance of panty shots in the entire series.
Malcolm in the Middle had one where Lois joined a book club which was just an excuse for them to behave badly.
Thirty Rock's Liz joined a similar club but it was really a Fight Club.
Farscape had "Bringing Home the Beacon" in season 4, following the guy-only "Mental as Anything". The cast was reunited for the episode's finale.
Stargate SG-1 has an episode "Hathor" where the female members of the SGC have to rescue the men from Hathor, who has brainwashed all the men of the base except for Teal'c, who is protected by his symbiote. Unfortunately, it is regarded as one of the worst episodes of the series and has actually become Canon Discontinuity, and later episodes simply mix the men and women together in episodes that take skills and abilities from the entire cast.
Leverage had this in an episode appropriately titled 'The Girl's Night Out Job.'

Video Games

One of the Dream Scenarios in Warriors Orochi 2 features a Charlie's Angels parody where you play as No, Zhen Ji and Xiao Qiao, off to rescue all the other female characters who have been kidnapped by The Tyrannical (and lecherous) Dong Zhou. Basically every female character in the setting is involved... along with Zhen Ji's husband, Cao Pi, who is so Bishonen he got mistaken for a girl and kidnapped. As he puts it, "This will take a while to live down..."
- Come to think of it, Ranmaru Mori is also involved, though he doesn't do much other than guard your main camp. Also, he's more girly than most girls, having dropped several Bridgets in his time, including getting hit on by Magoichi Saika.
One of Crimson Viper's quotes to Rose in Street Fighter IV is an invite to a "Ladies' Night".

Web Comics

The "Girls' Night Out" Story Arc from Sluggy Freelance quite surprisingly uses this trope.

Web Original

The entire series of Gotham Girls was basically a girl's night out. Especially in the third season when literally every man in town vanished.
The Descendants, in the issue 'All Girls Like the Bad Boys' (no relation), the only two male regulars appearing at put under Mind Control, leaving most of the female cast to fight them, whether they have powers or not.
In the Paradise setting, this is slightly subverted in that, in the story occasions in which female characters take a night out ("Election Fever", "Family Tree"), it is frequently in order to help someone involuntarily female get comfortable in her new femininity.
Nowhere near resulting in respect, but The Nostalgia Chick's review of The Little Mermaid resulted in a females-only crossover (and fangirl sing along) where they all tried to try and get her to like the movie.

Western Animation

"Girl's Night Out, " the aptly named episode of The New Batman Adventures where Batgirl and Supergirl team up to take on Livewire, Harley Quinn and Poison Ivy. An earlier TAS epsiode Batgirl Returns focused largely on the young heroine sleuthing alongside Catwoman. Batman has all of two lines, though Robin is present in a supporting role.
In Danny Phantom, Danny and Jack went off on a Disastrous Fishing Trip, while Spectra, Kitty and Ember used their powers to make all the men in Amity Park disappear, leaving Sam, Jazs and Maddie to fight them and save everyone. Again, the episode was called Girl's Night Out.
In the Teen Titans episode "Switched," Cyborg, Robin and Beast Boy are turned into puppets, while Starfire and Raven have to save them, while stuck in each other's bodies. An interesting example, since the focus was less on the genders of the protagonists and more on them being generally Different As Night and Day.
In the Star Trek: The Animated Series episode The Lorelei Signal, the men were seduced and kidnapped by female aliens, and Uhura and Chapel led an all-female team to rescue them—the only occasion on which Lieutenant Uhura has been seen in command of the Enterprise.
The Justice League episode "Fury". The supervillainess Aresia's attempted Gendercide has left all the male superheroes sick and unable to fight, so it is up to Wonder Woman and Hawkgirl to stop her. Justice League Unlimited also had the episode "Grudge Match," where the villainess Roulette puts female heroes under mind control and has them fight each other in her arena. Huntress and Black Canary (Shout-Out to the Birds of Prey comics title here) have to unravel the plot and save all of the heroines under Roulette's control.
The animated G.I. Joe series had this as well, the plot being that somehow, COBRA had gotten their hand on a conch that only affected men (it hypnotized them), leaving only the women to fight them off. Invoked by both sides, since the Baroness and a handful of the rarely seen female Cobra soldiers were perpetrating most of COBRA's schemes by necessity.
Evie from the animated series of The Mummy had to save her husband, son, and cousin from a siren in one episode, because only females were immune to this siren's song.
X-Men: Evolution episode "Walk on the Wild Side" might count. The guys aren't actually gone, but the whole plot of the episode revolves around Jean, Shadowcat, Rogue, Magma and Boom-Boom forming their own vigilante team called the Bayville Sirens. Cyclops and Nightcrawler secretly follow them (even helping them with an unseen optic blast), but decide against jumping right into the fray, learning An Aesop that the girls are just as capable as the guys.
The Aladdin series had multiple episodes focusing on Jasmine. Aladdin is present in every episode (duh, look at the title) but Jasmine has saved his life at least once and even got a chance to save the entire city of Agrabah by herself.
- She looks good with a whip as Scourge of the Desert. Evil Is Sexy.
The Simpsons episode "Marge on the Lam" is based on this trope in which Marge and Ruth Powers go on a girls night out.
Transformers Prime has "Predatory" where aside from Jack who spends nearly the whole ep needing rescue, the only other characters, (and only Transformers) are fembots Arcee and Airachnid. "Crisscross" again only has Arcee and Airachnid as the only Transformers with more than a quick silent cameo, although Jack again has a large role, and Agent Fowler makes a brief apperance, as does Silas.
The Young Justice episode "Secrets," where Artemis and Zatanna go out on a night of crime-fighting, only to be attacked by the psychotic Harm. They wind up getting help from a third female, Secret/Greta Hayes. The male teammates (and Megan) also appear, but only in a pair of side-plots.
- The second season episode "Beneath" continues the trend, focusing on Batgirl, Bumblebee, Wonder Girl and Miss Martian. There's a subplot involving Blue Beetle and a few brief appearances from Nightwing, but the vast majority of the focus is squarely on the ladies.