Fascists' Bed Time

"A Militsya patrol stops a passerby a few minutes before the curfew (they're under martial law). They check his documents and everything seems to be in order, so they let him go. But when the man turns to leave, one of the officers shoots him in the back. "What the... why'd you do that!?" his colleague exclaims. The first officer shrugs. "Oh, I know where he lives. There's no way he's getting home before the curfew.""

- Old Polish joke

Curfew: the piece of martial law no self-respecting dictatorship can go without. Specifically: a curfew on everybody, often at an unreasonable time, enforced by burly if not overly observant guards.

Curfews are a good early sign that a government is controlling people's lives, so they're useful as a sign of benign government turning into a cruel regime. Narratively speaking, the authorities can say that someone is a rebel just for being about, and mean characters can fight in major urban areas without risking innocent lives.

A common feature of a Dystopia.

Comics

 * In V for Vendetta, Evey gets in trouble with the Fingermen over prostitution. And curfew. Toned down to just curfew in the film.
 * Bluto and the Commodore had one over the town in Popeye.
 * Cal instituted such a curfew during his reign as Chief Judge in Judge Dredd.
 * As did the Dark Judges during the Necropolis arc. They tried to discourage people getting shot as "there are so many more interesting ways to die."
 * In one Sonic the Comic story, set when Robotnik was still ruler of Mobius, badniks started declaring new, asinine laws around a town, including a curfew set at a time that had already passed, meaning everyone broke the law retroactively.

Film

 * In Xchange, everyone is required to carry a dogtag, fitted with a trackable chip, apparently replacing plastic and paper IDs. It is illegal to be out after curfew, if you don't have a proper tag. It is never revealed what the punishment is, though. The government is not a dictatorship, though.

Literature

 * A City In Winter—enforced by death, no less
 * Ankh-Morpork experienced this under the rule of Homicidal Lord Winder as seen in Night Watch; it may have occurred under other Patricians as well.
 * In contrast, Lord Vetinari dislikes curfews. They're bad for business.
 * Occurred in Harry Potter and the Deathly Hallows—just in Hogsmeade, though, as it's the only all-wizarding settlement (not for lack of trying on Voldemort's part).

Live Action TV

 * The Doctor Who story The Happiness Patrol.
 * The episode "Rise of the Cybermen" shows a curfew in the parallel world, but no indication that there's anything wrong with the government.
 * Mentioned as part of President Clark's declarations as he seizes power in Babylon 5.

Tabletop RPG

 * In Misspent Youth by Robert Bohl, a game where you play a group of teenage anarchists out to change the world, the group creates Systems of Control that are sci-fi-ish details about the world that The Authority uses to mess with your lives. As in the real world, the authorities frequently use curfews to control children.

Video Games

 * You first gain control of the main character of Zork: Grand Inquisitor seconds before the town's curfew goes into effect.
 * In the Konquest mode of Mortal Kombat Deception, the main character returns to meet his former ally and all-around Knight Templar Hotaru in the town he's just conquered, only to be arrested for breaking curfew. Judging by appearances, he is held in a cell awaiting trial for over a decade.
 * One of the options in political simulator Democracy 2. It will take a lot of political influence and it will make you unpopular very quickly.
 * In Quest for Glory 2, it's against the law to be out at night in the fascist city of Raseir, fallen twin to the free city of Shapeir.
 * Deus Ex features a curfew in Paris now that it's under martial law, enforced by twitchy military robots.
 * A fan-made prequel and Game Mod 2027 features Moscow under martial law. Police and bots will shoot at anyone caught out after dark.
 * The online video game The Curfew is about a future Britain where this (unsurprisingly) has happened.
 * In Metal Gear Solid 4: Guns of the Patriots, the town in which chapter 3 takes place is under a very strict curfew, anyone caught outside after a period of time is arrested (or in Snake's case, shot at) under suspicion of being part of La Résistance, naturally you have to tail a resistance member who's breaking curfew, what else were you expecting?
 * In Dragon Age II, hallmarks of Meredith's reign as Templar Knight-Commander apparently include curfews and midnight raids on families suspected of sheltering mage relatives. It doesn't stop Hawke and co. from going wherever they please, but most of Meredith's methods tend to do more damage than they prevent.

Western Animation

 * The episode of The Simpsons "Wild Barts Can't Be Broken" revolved around an enforced curfew for minors after being blamed for vandalizing Springfield Elementary (though unbeknown to the police, it was a drunk Homer, Lenny and Carl who were the culprits). In retaliation,.
 * Fire Nation-occupied settlements in Avatar: The Last Airbender.
 * In The Legend of Korra, Tarrlok's idea of a sane response to anti-bending revolutionaries is to impose curfews on every non-bender in Republic City. Taking this a step further, he shuts off the electricity to a whole district just to goad them outside, where he can accuse them of breaking curfew and have them rounded up.
 * In Transformers Animated, new leader wastes no time in establishing a curfew on Cybertron, allegedly to protect against the looming Decepticon threat.
 * In an episode of Darkwing Duck, Gosalyn is sent to the future, where the Gosalyn-less Darkwing has become a vicious dictator called Darkwarrior who does this. Gosalyn even notes "Only my dad would set a universal curfew at 8 o'clock."
 * The Mirror Universe in the Superman the Animated Series episode "Brave New Metropolis".

Real Life

 * Real Life: Dictatorial regimes have in fact been known to do this. Augusto Pinochet is said to have enforced his curfew with snipers. Mubarak tried it in Egypt recently. It was quite ignored indeed.
 * Not only dictators, the Americans did it in Iraq too. Curfews are an effective counter measure against insurgencies or when you're expecting trouble.
 * In the more repressive cities in America they have one for anyone they think is under 18. There have been reports of the government doing this for everyone in a city down south.
 * In some states, the laws for new drivers under 18 often include a curfew, usually 11 PM or midnight. Though there are exceptions made for those driving because of emergencies, school/religious functions, or because they are licensed EMTs.
 * In some of those states, there's also an exemption for kids who have jobs, as long as they get their parent(s) and boss to sign a waiver.
 * This was actually a historical and very grim way racial segregation was enforced in the US. A "sundown town" was one in which minorities were explicitly not safe after dark. Minorities could not buy land in these communities, and being caught in them after dark could lead to harassment, expulsion, or even lynching, sometimes at the hands of local law enforcement. This phenomenon was not limited to Southern white-on-black oppression - the technique was used against blacks, Native Americans, Jews, and Chinese minorities, and the state with the most confirmed cases of the phenomenon was Illinois.
 * Also happens on occasion for more reasonable cases where a city is struck by a riot or an increase in violent crime.
 * One noteworthy Real Life example occurred during the Jewish rebellion against British rule in the League of Nations Mandate of Palestine in 1947: in an effort to regain control, the British authorities imposed a 24-hour curfew, meaning that Jews were simply not allowed to go outside at all. This still didn't work.