[[caption-width-right:300:''Enemy spotted!'']]

The most popular online FPS in the world, with some claiming it generates more Internet traffic than the whole of Italy.

It's a terrorists versus counter-terrorists modification for ''VideoGame/HalfLife1''.

It pretty much has no plot beyond "counter-terrorists must kill the terrorists and vice-versa" though there are game modes fitting the theme beyond death match such as "bomb defusal" (the only mode played in competitive matches), "rescue the hostages" (played on public servers essentially) and "escort the VIP" (never played). Various custom game modes have been introduced since: modes that limit you to specific weapons selections, modes with special, often gimmicky goals, and even maps where the object isn't to kill the opposing side but rather to navigate the map in a maze-like fashion.

Originally a free GameMod, Creator/{{Valve|Software}} (the developers of the original ''Half-Life'' and its sequel, ''VideoGame/HalfLife2'') has since hired on the original developers to create ''Counter-Strike: Source,'' using ''Half-Life 2's'' graphics and physics engine.

It gets a great deal of the world's top gamers with many long standing competitive scene to this day. It also gets a great deal of the idiots, and also MoralGuardians who [[ComplainingAboutShowsYouDontWatch rail against it]] for "[[MurderSimulators teaching kids to kill]]." Most memorable being the instance of a high school student expelled for basing a Counter-Strike map off of his school. In addition, a judge in Brazil has banned Counter-Strike sales throughout the country, because of a map designed as Rio De Janeiro. Not that it helped, as the game is widely pirated in Brazil.

Namco released an adaptation of Counter-Strike for Japanese-based arcades called ''Counter-Strike Neo''. It was officially published by Namco in 2005 under the [=GoldSrc=] engine. In addition, Namco released a visual novel companion called ''White Memories'', which gives [[AllThereInTheManual more background details to the world of CS Neo and the reasons why the conflict between the CSF and NEO started]], as well [[AllThereInTheManual as giving out information on all characters involved]]. Unfortunately, the site hosting the [=VN=]s closed down in the mid 2000s with a partial translation of only 6 out of 12 episodes.

A new version of Counter-Strike, subtitled ''Global Offensive'' came out in August 2012. [[http://www.youtube.com/watch?v=edYCtaNueQY You can watch its Source Filmmaker Trailer here]].
!!Includes examples of:

* AKA47: Though there's an unofficial patch that (mostly) corrects this. Earlier versions of ''Counter Strike'' did use the real names for guns.
** Some details: There was a time (pre-{{Steam}}) where which weapon names you got depended on whether you had the mod version, which required ''VideoGame/HalfLife1'' to play (real names) or had bought the stand-alone retail version of Counter-Strike (fake names). The mod version also is the origin of the aforementioned "unofficial patch" (titles.txt).
** Depends on regions in ''Counter-Strike Online''. Korean, Japanese and Taiwan versions straight up calls them by their original name, but Malaysian/Singapore and Indonesian versions calls it by Condition Zero titles to ease up the localization work.
** Mostly averted in Global Offensive. Most guns are called by their actual names (although without the weapon manufacturers,) with the exceptions of the sawed off Remington 870 and the Taser. The Taser uses this trope (as Taser is a brand-name,) being named the "Zeus x27," while the sawed off Remington 870 is simply called the "Sawed-Off Shotgun." A few other weapons use names that are close to but not quite their real names (the Sig SG 556 is the "SG 553", the FN SSR is the "SCAR-20", and the AI Arctic Warfare still has its infamous "AWP" moniker).
* AnnouncerChatter: an ''extremely'' common server-side mod will make the game announce a "KILLING SPREE!!!", a "M-m-m-m-monster kill!!!", a "Headshot!", or a "HUMILIATION!!!" (knife kill), taken from Quake and VideoGame/UnrealTournament.
** Took until Counter Strike: Source to disable this MostAnnoyingSound.
** Some servers take this to a fascinating extreme, uploading dozens of sound clips to your computer when you first enter them.
** Counter-Strike Online have their own Announcer Chatter, from the standard multiple kill announcements to UT-like voice clips. Special mention goes to the nearly-haunting 10-second countdown in zombie mode.
* ArmorIsUseless: You can buy a helmet, vest, or both. They barely lessen the damage taken - they're the difference between five bullets killing you and four bullets killing you. Realistically, though, the armor is more effective against most of sub-machine guns and pistols (except the Deagle, Five-Seven, and Tec-9) than against heavier arms and also protects well against grenades.
* ArtificialStupidity: Unfortunately, ''Global Offensive's'' bots dip into this in some aspects. Counter-Terrorist bots often refuse to go near one bomb site despite knowing the other site is clear, Terrorist bots will only use one of the two bomb sites on a few of the maps, bots on both teams will step in front of your shots, refuse to shoot enemies until they get shot first, hit you with a High Explosive grenade despite knowing that there's no enemy nearby, or even '''shoot at a Decoy Grenade'''... but perhaps worst of all is that it's completely arbitrary whether a bot will listen to any of your in-game callouts, to the point where they'll even voice their refusal [[TooDumbToLive even at the expense of their own lives.]]
* ArtisticLicenseEconomics: The short-lived attempt by Valve to dynamically price the guns - basically, trying to balance the game by having popular weapons get more and more expensive while making bad guns cheaper than dirt. At one point, a gun somehow cost '''negative''' money.
* BackStab: The slower, more damaging stab attack with the knife gains the ability to OneHitKill when it hits the enemy in the back.
* BankRobbery: The setting of the 'Bank' and 'Downtown' maps in Global Offensive. Also, 'Miami' from the Xbox version of Counter-Strike. And the 'Miami Heat' mission from Deleted Scenes.
* BoomHeadshot: [[PurePwnage FPS Doug]] said this while playing Counter-Strike, making it ''the'' TropeNamer.
* BoringButPractical: Flashbangs.
* CherryTapping: Knife kills, though it has the advantage of being a one-hit kill when stabbing someone in the back.
* [[TVTropesWillRuinYourLife Counter-Strike Will Ruin Your Life]]: Amount of time spent playing (with some exceptions) correlates with percentage of vocabulary replaced with "AWP SUX/ROX", "[=N00B=]", "FAG", etc.
* CosmeticallyDifferentSides: {{Subverted|Trope}}. Although both teams share many items (pistols, submachine guns, grenades and armor) and could end the game by duking it out in a deathmatch, the significant equipment and tactics revolve around objectives that serves as one team's antithesis to the opposing team's war doctrine.
** Terrorist weapons are cheap and loud to suit very aggressive play while Counter-Terrorist weapons are expensive and optionally silenced to encourage some really devious stealth tactics.
** The {{metagame}} in Classic game rules dictates that one team, the aggressors, initiate the match and attempt to win it early while the other, the retaliators, quell the incoming attack or, if pressed, hope to hold the aggressors off until the timer expires. In "defuse" scenarios, Terrorists plant bombs on targets and Counter-Terrorists defuse them. In "hostage" scenarios, Counter-Terrorists rescue hostages and Terrorists resist them.
* DoNotRunWithAGun: Running while shooting will send your bullets anywhere that isn't the reticule. How much it throws off your aim is proportional to movement speed: for most of the series velocity was lost immediately after you let go of the arrow keys, letting you shoot and run all but simultaneously. In ''Global Offensive'' reaching a stop takes a fraction of a second, but can be done faster by tapping the direction arrow opposite to the direction you were moving in.
* ElaborateUndergroundBase: For all intents and purposes, the raid on a well-armed gang in ''Modesto'' of all places goes awry - you, a SWAT member, fall into a huge ''warehouse under a crime-ridden slum'' filled with crack for shipping and weapons.
* EscortMission: The hostage maps, though most opt to kill the opposing team instead of saving the hostages there.
** Averted in Global Offensive, as the [=CTs=] carry the hostages over their shoulder from one set point on the map to the other. Also, only one hostage of two (each in separate locations) needs to be saved. It was originally played straight (see below), but was eventually changed.
** The [=CTs=] can claim victory on a hostage map by rescuing two hostages and then executing the other two. This is, of course, highly discouraged.
** The V I P mission mode that was a feature of 1.6 but was never very popular.
* EvilVersusEvil: The two terrorist factions fighting over the radioactive material in Deleted Scenes.
* GameMod: In addition to the fact that this game is the most successful mod ever, custom content is very popular; note that [=GameBanana=] has [[http://www.gamebanana.com/skins more Counter-Strike: Source skins]] than it has skins of ''any other game combined''.
* GunsAkimbo: Dual Beretta Elites. More useful than you think they are. In fact, they're the second most used, right below the Desert Eagle.
* GunPorn: An update for ''Global Offensive'' has added weapon skins and crates, but above all, pressing a button while ingame will deploy a special animation of the player inspecting the weapon. Even better, considering there's now a loadout screen where one can view each weapon and skins, complete with a fully three-dimensional render and pan of said weapons. Third-party mods can also give the player a nice set of fancy new weapons, replacing your boring old M4 with [[RareGuns something like an XM8 or tricked-out variant.]]
* HeroicSacrifice: In ''Deleted Scenes'', the Spetsnaz commanding officer stays behind to make sure none of the warring terrorists disable the bomb you planted to destroy the nuclear core.
* HolidayMode: As of December 18, 2013, ''Global Offensive'' has one. It features falling snowflakes on the main menu, chickens wearing antlers and Santa hats, and the cables on Lake have Christmas lights.
* InformedEquipment: Most Terrorists player models visibly wear no armor and even fewer have helmets, while most Counter-Terrorists wear both. But playing as either you have actual protection from armor and helmets if and only if you buy it at the beginning of a round.
* LeeroyJenkins: Just go on the online games. ''No one'' works together, unless they're in clans.
** Somewhat averted for Console ''Global Offensive'', where players are made to work together via forcing them into game chat at all times.
* LeetLingo: Something of a TropeCodifier for it. In the wee early days of Counter-Strike 1.6, it was a major stereotype that nearly all chat consisted of l33t sp33k1|\|6 asshole children.
* LightningGun: ''Global Offensive'''s Zeus x27 ([[AKA47 A.K.A. Taser]]) is a short range OneHitKill {{Throw Away Gun|s}}, regardless of where you hit your target.
* LuckilyMyShieldWillProtectMe: The Counter Terrorist's buyable equipment in Condition Zero includes a solid metal riot shield that takes up your primary slot and secondary weapon in return for blocking all forms of harm in the front while it's equipped. The first multiplayer game to use this, and it was ''absolutely hated'' by pros.
* ObviousRulePatch: In ''Global Offensive'', players who commit suicide, whether accidentally or not, no longer receive any cash for that round, in an attempt to stop "denying" a la DOTA (a technique in which a player kills themselves or friendly units to prevent the enemy from receiving bonus cash for killing them).
* OneBulletLeft: Invoked. Killing an enemy with the last bullet in your mag nets you a Steam achievement.
* OneHitKill: The [[GameBreaker AWP Sniper Rifle]] is a one shot kill anywhere but the leg. Banned from pubs and the only weapon that can compete with the AK-47, which always has perfect accuracy on its first shot.
* OutOfTheInferno: In ''Global Offensive'' having friendly fire off lets your teammates happily walk through the flames created by your incendiary grenade/Molotov cocktail. Otherwise, however, going out of them will be anything but badass as it slows you down while damaging you, forcing you to hobble for your life.
* {{Qurac}}: de_dust and de_dust2, and the level ''Recoil'' for ''Deleted Scenes''.
* RightHandedLeftHandedGuns: Completely enforced until Global Offensive, where for the very first time in the series, there are properly-modeled weapons for right-handed users.
** Some weapons in Counter-Strike Online were actually mirrored correctly.
* RightWingMilitiaFanatic: Presumably the Militia skin for the Terrorist, and the map cs_militia.
* SawedOffShotgun: Comes in three flavors, Double Barrel and the Quadbarrel for ''Counter-Strike Online'', and a sawn-off Remington 870 in ''Global Offensive''.
* ShoutOut: The manga store in the Japanese Subway level of ''Deleted Scenes'' references ''Anime/ReadOrDie'' amongst other manga, and the after-credits to ''Film/DrStrangelove''.
** The "1337 Krew" terrorist skin is a reskin of Gordon Freeman from ''Half-Life'' (of which the game is a mod of).
** The gang leader in "The Turn of the Crank" wears [[Film/{{Scarface}} a white suit, trades in drugs, speaks with a heavy Cuban accent, and is coked up in the final battle, making him hard to kill. He screams at you all the way, and you breach the room he's hiding in with explosives.]]
** "Recoil", being set in Northern Africa and fighting off Jihadi after being shot down in an RPG, being a member of Delta Force and picking up a standard sniper... we'll give you two seconds. TIME'S UP! ''Film/BlackHawkDown''.
* ShownTheirWork: [[http://i.imgur.com/SnQmy.jpg Way too much?]]
* StandardFPSGuns
** Handguns in CS deserves special mention, being able to go toe-to-toe against full sized guns when in skilled hands.
* SticksToTheBack: At least one counter-terrorist player model in ''Global Offensive'' inverts this: rifles stick to the front when unequipped. For other games the unequipped weapons just don't appear at all.
** Played straight in ''Source'', however.
* SuperSenses: Hearing, specifically. A good player can find a nice little place to hide in, hear some footsteps, and instantly blurt out to his team "3 coming long A."
** In competitive play this can lead to players trying to "out-sound" each other, mixing walking with running to fool enemies of their position.
* TerroristsWithoutACause: The terrorists don't really have a mission in the normal game. Their backgrounds posit them as anti-government, anti-Western fanatics.
** Averted in ''Condition Zero: Deleted Scenes''. Some of the terrorists who are present in multiplayer actually have goals and causes (not all of them are present, though).
* ThrowAwayGuns: A sometimes effective strategy, both offensively (for {{Leeroy Jenkins}}es) and defensively (No time to reload because the enemy is rushing you? Throw away your gun and grab a dead guy's gun!).
** Alternatively, you can throw your pistol as if it was a grenade, [[http://www.pcgamer.com/2013/04/22/csgo-sleight-of-hand-watch-this-incredible-flashbang-fakeout/ which works, too]].
** There's an achievement for donating enough guns to teammates in this fashion in ''Global Offensive''.
* TranslationConvention[=/=]JustaStupidAccent: In ''Deleted Scenes'', all characters speak English [except for the opposing side], however accented.
* VideoGameCrueltyPotential: You can shoot, knife, throw grenades at, or even (in all games but ''Global Offensive'') kill hostages...
** VideoGameCrueltyPunishment: ...but doing so nets a SERIOUS cash penalty, meaning that you're going to suffer for quite a few rounds as a result.
* WesternTerrorists: Midwest Militia, Arctic Avengers and Phoenix Connexion are from America, Sweden(!) and former Soviet Union states in Eastern Europe respectively. Averted with the Leet Crew and Guerrilla Warfare.
** Averted (again) in ''Deleted Scenes'', which features Jihadi, Filipino rebels, Japanese and Russian terrorists, bank robbers, and so on.
* ZombieApocalypse: Comes in two flavors - Infection (which came before the ''Franchise/{{Halo}}'' game mode), wherein one guy gets infected and must run around and kill the others or where the humans must escape, and NOTD/Zombie Riot, where survivors fight off an army of CPU-controlled zombies. The former usually has nigh-invulnerable zombies and forces players to hole up in buildings and last as long as possible (or escape an area), and the latter is the standard "needs a headshot" kill.
** Counter-Strike Online recycles the mods above and made it to their official playlist as Zombie Mode (Infection) and Zombie Scenario Mode (NOTD/Zombie Riot).
** A poor-man's zombie mode can be done by making it so a massive number of bots (unofficial or not) join the opposing team and are only allowed knives. In fact, this is how Turtle Rock studios got the inspiration to make ''VideoGame/Left4Dead''.