The term "action" has two or three slightly different meanings in Dominion.
 Action cards
Action cards are a type of card. The large majority of Kingdom cards are Action cards. By default, unlike Treasure cards, each player may play only one Action card on a turn; however, many Action cards provide you with the right to play additional Action cards on the same turn. Action cards may have a wide variety of effects, from vanilla bonuses to attacking other players to rearranging cards in the deck.
Action cards are frequently referred to simply as "Actions"; whether the term "Action" refers to Action cards or the meaning below is usually clear from context.
Action cards have "Action" written on the bottom, and they ordinarily have a white border, unless another type (Reaction, Duration, Ruins, Reserve) supersedes that. If an Action card also has another fundamental type (Victory, Shelter), the border is split between white and the color of the other type.
 Actions remaining
A player starts their turn with the right to play only one Action card from their hand. Some Action cards, however, grant +1 or more Actions when played, allowing a player to play additional Action cards on the same turn. This is referred to as increasing that player's "number of actions" available.
 Action phase
The Action phase is one of the three phases of a turn of Dominion. It begins a player's turn and is the only phase in which they are permitted to play Action cards. The rule book describes the Action phase as follows:
- In the Action phase, the player may play one Action card. Action cards are the Kingdom cards that say “Action” at the bottom of the card. Since players do not start the game with any Action cards in their initial Decks of 10 cards, a player will not have any Actions to play during his first 2 turns. Normally, a player may play only one Action card, but this number may be modified by the Action cards that the player plays.
- To play an Action, the player takes an Action card from his hand and lays it face-up in his play area. He announces which card he is playing and follows the instructions written on that card from top to bottom. The player may still play an Action card even if he is not able to do everything the Action card tells him to do; but the player must do as much as he can. Furthermore, the player must fully resolve an Action card before playing another one (if he is able to play another Action card). Detailed information about card abilities can be found in the card descriptions at the end of these rules. Any Action cards played remain in the player’s play area until the Clean-up phase of the turn unless otherwise indicated on the card. The Action phase ends when the player cannot or chooses not to play any more Action cards. Generally, a player can only play Action cards during the Action phase of his turn. However, Reaction cards are an exception to this rule as they can be used at other times.
One card, Villa, can return the player to their Action phase from their Buy phase.
 Cards that interact with Action cards
Cards in italics have been removed.
- Dominion: Throne Room, Library
- Intrigue: Lurker, Shanty Town, Conspirator, Ironworks, Replace, Tribute
- Alchemy: Transmute, Vineyard, Scrying Pool, University, Golem
- Prosperity: Quarry, Rabble, King's Court, Peddler
- Cornucopia: Farming Village
- Hinterlands: Scheme, Inn
- Dark Ages: Death Cart, Ironmonger, Procession, Rats, Wandering Minstrel, Band of Misfits, Cultist, Graverobber
- Guilds: Stonemason, Herald
- Adventures: Coin of the Realm, Champion, Disciple, Teacher, Magpie, Port, Royal Carriage, Ferry, Plan, Seaway, Lost Arts, Training, Inheritance, Pathfinding
- Empires: City Quarter, Overlord, Bustling Village, Emporium, Enchantress, Gladiator, Fortune, Sacrifice, Crown, Advance, Arena, Colonnade, Defiled Shrine, Orchard, Triumphal Arch
- Nocturne: Imp, Leprechaun, Magic Lamp, Haunted Mirror, Conclave, Devil's Workshop, Necromancer, Zombie Apprentice, Tormentor, The Swamp's Gift, Famine, Fear
- Promo: Sauna/Avanto, Walled Village, Prince, Summon
 In other languages
- Czech: Akce
- Dutch: Actie
- Finnish: Toiminta
- French: Action
- German: Aktion
- Italian: Azione
- Polish: Akcja
- Russian: Действие (pron. dyeystviye)