The best large-group card game that I know of is Up and Down the River , which Wikipedia knows as
Oh, Hell .
I find the rules given by Wikipedia to be confusing, though, and found a better set here at eHow .
(Note that both of these rulesets differ slightly from the version I'm familiar with, as there are endless variants of most of these games.)
boardgames.stackexchange.com/users/156/JSBձոգչ
Eleusis
This is one of my favourite card games.
You have to use inductive reasoning to figure out the dealer's secret rule.
It's actually better with a large group because you learn more from other players' mistakes while waiting for your turn to come around.
It can be a bit intimidating for new players, so you might want to start with a small group playing Eleusis Express to get the hang of it.
boardgames.stackexchange.com/users/118/Don Kirkby
If you have enough players (8+) you can play werewolf with playing cards: Clubs 2-9 ==
Wolves Hearts 2-9 ==
Villagers Jack of clubs ==
Hunter Jack of diamonds ==
Thief Queen of hearts ==
Cupid Queen of spades ==
Witch King of diamonds ==
Seer Ace of Spades == Mayor marker
boardgames.stackexchange.com/users/45/Toon Krijthe
Many poker variants, including the very popular Texas Hold'em , can support a large number of players.
In Texas Hold'em, each player is dealt only two cards of their own, there are 5 community cards, and 3 burn cards, meaning that you could in theory support 22 players if you deal out all of the cards, though generally you play with 10 or fewer players on a table, maybe up to 12 or so.
It does require something to bet with—chips, pennies, stones, dried beans, or any other form of counter—so it can't be played with just a deck of cards, but usually it's pretty easy to find some kind of betting counters.
If you don't like gambling, you can play it as a tournament, in which each person gets a fixed number of chips and the last player left with chips wins.
boardgames.stackexchange.com/users/112/Brian Campbell
You can find lists of card games for different numbers of players at pagat.com .
In particular, Looking for Friends (找朋友) looks interesting, though I haven't tried it.
It's described as a trick-taking game that works well with large groups.
boardgames.stackexchange.com/users/118/Don Kirkby
Mao can work well with large numbers of players, or you can open a few more decks and get several different games going in the same room.
It's also an intriguing game to watch, for those who don't understand how to play.
boardgames.stackexchange.com/users/1609/Eric
Hearts (yes, similar to the Microsoft game) works surprisingly well with 8 people and 2 packs: I've not tried with more, but there's no theoretical reason why not .
Racing Demon (one pack per person) is also good, if a little raucous with high numbers.
boardgames.stackexchange.com/users/1644/Tim Lymington
Creights is a very engaging, Uno-like party game played with a standard deck.
It is about 70% luck and 30% skill, in my estimation.
It scales easily to about 7-8 players, but requires two decks shuffled together with 5/6+ players.
It doesn't require those two decks to have the same backs, but make sure to remove a couple of 5s from the deck if you play with two decks.
boardgames.stackexchange.com/users/172/Drew Hoskins
Liar is simple, requires some tactics to have a chance to win and can be played by all ages.
boardgames.stackexchange.com/users/309/eric
What card games work well with a large number of players (say 6+ players) and only require a standard pack of playing cards?  I'm particularly interested in games where the rules can be explained fairly quickly, but there is still a reasonable level of tactics.  Also it would be preferable if the game can be played in a single room.  One game per answer please.
What games are suitable for a large number of people with only a pack of playing cards?
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boardgames.stackexchange.com/questions/1107
boardgames.stackexchange.com/users/122/tttppp
Many poker variants can support a large number of players. You can also try Mao, Hearts and Racing Demon. One of the best large-group card games is  Up and Down the River. If you have enough players (8+) you can also play werewolf with playing cards.S0: In addition, many poker variants, including the very popular  Texas Hold'em , can be played with a large number of players. Mao  can work well with large numbers of players, and Hearts also works surprisingly well with 8 people and 2 packs. Racing Demon is another game that works well.  Liar is simple game that requires tactics nd can be played by all ages.

One of the best large-group card games is  Up and Down the River. If you have enough players (8+) you can also play werewolf with playing cards.S0: In addition, many poker variants, including the very popular  Texas Hold'em , can be played with a large number of players. Mao  can work well with large numbers of players, and Hearts also works surprisingly well with 8 people and 2 packs. Racing Demon is another game that works well. S0: Liar is simple game that requires tactics nd can be played by all ages.