The term "action" has multiple different meanings in Dominion:
- Action cards – a card type.
- Actions remaining – a resource, how many Action cards is a player allowed to play.
- Action phase – a phase of each turn in which the active player can play Action cards.
 Action cards
Action cards are a type of card. By default, unlike Treasure cards, each player may play only one Action card on a turn; however, many Action cards (and a handful of other effects) 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, Treasure, Shelter, Night), the border is split between white and the color of the other type.
As of the release of Plunder, approximately 84% of Kingdom cards are Actions; the expansions with the lowest density of Action Kingdom cards are Nocturne, which has a focus on Night cards as one of its main themes, and Prosperity and Plunder, which have a focus on Treasure cards. Several non-Kingdom Action cards also exist, which can be accessed through the effects of various other cards or card-shaped things; these include Ruins, Horses, Zombies, Wishes, the successors to Travellers, and a handful of others.
 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 Action or +2 Actions (in some cases even more) 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 cards that have this effect are called non-terminal, while Actions that do not grant +1 Action (or more) are terminal. A deck that has the ability to play multiple terminal Action cards on a turn is said to have increased terminal space. Villagers can also be used to grant +1 Action, as well as a handful of effects from other card-shaped things.
 Action phase
The Action phase is one of the four phases of a turn of Dominion. It begins a player's turn and is typically 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.
Villa, Cavalry, and Launch can return the player from their Buy phase to their Action phase.
 Cards that interact with Action cards
A very large percentage of all cards in Dominion are Action cards, consequently, there are also many cards that interact with Action cards in one way or another. Cards in italics have been removed.
 Cards that play Action cards
- Dominion: Throne Room, Vassal
- Alchemy: Golem
- Prosperity: Crystal Ball, King's Court
- Dark Ages: Band of Misfits
- Guilds: Herald
- Adventures: Disciple, Royal Carriage
- Empires: Overlord, Crown
- Nocturne: Imp, Conclave, Necromancer
- Renaissance: Piazza, Innovation, Citadel
- Menagerie: Mastermind, Delay, Gamble, Toil, March, Way of the Turtle
- Allies: Courier, Royal Galley, Contract, Elder, City-state, Market Towns
- Plunder (expansion): First Mate, Spell Scroll
- Promo: Sauna/Avanto, Prince, Summon, Captain
 Action gainers
These are gainers that can (only) gain Action cards.
- Lurker, University, Procession, Stonemason, Disciple, Advance, Populate, Acolyte, Specialist, Sunken Treasure, Swap, Woodworkers' Guild
- Death Cart, Cultist, and Marauder gain Ruins.
- Rats, Magpie, Port, and Experiment gain additional copies of themselves.
- For Horse gainers, see here.
- Transport does not gain cards but lets you acquire Action cards in a similar manner.
- Spell Scroll, Rush, Mirror, Invasion
 Action trashers
These are trashers that can (only) trash Action cards.
- Lurker, Death Cart, Procession, Graverobber, Advance, Zombie Apprentice, Animal Fair, Acolyte, Woodworkers' Guild, Spell Scroll, Siren, Peril
 Cards that interact with Action cards that are played or in play
- Conspirator, Peddler, Scheme, Coin of the Realm, Champion, Emporium, Enchantress, Fortune, Colonnade, Improve, Horn, Lantern, Warlord, Fellowship of Scribes, Walled Village, Flagship, Harbor Village, Swamp Shacks, First Mate, Frigate, Tools, Inspiring
- All Ways.
 Cards that interact with Action cards in decks
- Library, Scrying Pool, Rabble, Farming Village, Wandering Minstrel, Famine, Border Guard, Hunter, Fortune Hunter, Mapmaker, First Mate, Fated
 Cards that interact with Action cards in hands
 Card that interact with Action cards in discard piles
 Cards that interact with Actions in the Supply
- Cards that add tokens to Action supply piles: Ferry, Plan, Seaway, Lost Arts, Training, Pathfinding, Teacher, Defiled Shrine
- Other: Quarry, Lurker, Inheritance, Gladiator, Transport, Invest, Swap, Cheap
 Cards that interact with Actions being gained
- Defiled Shrine, Colonnade, Academy, Gatekeeper, Invest, Siren, Stowaway, Taskmaster, Abundance, Wealthy Village, Hasty
 Cards that score through Action cards
 Cards where the effect depends on the type(s) of another card
These cards reference the type(s) of another card to determine their effect. They will have a different effect if the referenced card is an Action than if it is a Treasure.
 In other languages
- Czech: Akce
- Dutch: Actie
- Finnish: Toiminta
- French: Action
- German: Aktion
- Italian: Azione
- Polish: Akcja
- Russian: Действие (pron. dyeystviye)