DnD Opportunity Attacks Rules

Opportunity attacks represent one of the most tactically consequential mechanics in Dungeons & Dragons 5th Edition combat, governing how creatures punish enemies who attempt to flee their reach. This page covers the precise definition, triggering conditions, execution sequence, and limiting rules for opportunity attacks, drawing from the 5th Edition Systems Reference Document (SRD). Mastery of this mechanic shapes positioning decisions, retreat strategies, and melee engagement across every encounter type described in the full rules index.

Definition and scope

An opportunity attack is a special melee attack that a creature can make as a reaction when an enemy leaves its reach without using the Disengage action or a teleportation effect. Per the D&D 5th Edition Basic Rules published by Wizards of the Coast, the opportunity attack is triggered specifically by voluntary movement — not by forced movement, falling, or teleportation.

Scope matters here: the rule applies to any creature with a melee reach, whether that creature is a player character, a monster, or an NPC. It is not class-specific, feat-dependent, or level-gated. Every combatant in the game operates under this rule from the first session forward, making it a foundational element of the D&D combat rules framework rather than an advanced mechanic.

The reaction cost is critical to scope. Each creature has exactly 1 reaction per round, which resets at the start of that creature's turn. Spending the reaction on an opportunity attack means it is unavailable for other reaction-dependent abilities — such as the Shield spell or the Sentinel feat's secondary clause — until the next turn begins.

How it works

The execution of an opportunity attack follows a strict sequence:

1. Trigger: An enemy creature voluntarily moves out of the attacker's reach (typically 5 feet for most melee weapons, 10 feet for weapons with the Reach property).
2. Reaction declaration: The attacker immediately declares use of their reaction. This interrupts the triggering creature's movement at the point it left reach.
3. Attack roll: The attacker makes a standard melee attack roll against the triggering creature's Armor Class, following all normal rules detailed in attack roll mechanics.
4. Damage resolution: On a hit, damage is applied normally per damage and hit points rules, including applicable damage modifiers and bonus damage from features like Sneak Attack if conditions are met.
5. Movement resumes: Whether the attack hits or misses, the triggering creature may continue its remaining movement after the reaction resolves.

A creature with multiple attacks — such as a Fighter using Extra Attack — does not make multiple opportunity attacks. The opportunity attack is a single melee attack, not a full Attack action. This distinction separates it from the Action economy described in D&D action types.

Common scenarios

Understanding when opportunity attacks apply requires mapping the rule to the most frequently encountered tactical situations.

Retreating from melee: When a character surrounded by 2 goblins attempts to run to a healer, each goblin within 5 feet of that character's starting position can use its reaction to make an opportunity attack as the character's movement exits their reach. Both attacks resolve before the character reaches the healer.

Chasing down an enemy: A fleeing monster that moves past a paladin's reach triggers the paladin's opportunity attack. This is the primary deterrent to monsters disengaging without the Disengage action.

Reach weapons vs. standard melee: A creature wielding a polearm (reach 10 feet) triggers an opportunity attack at the 10-foot threshold, not the 5-foot threshold. This creates a layered threat zone that interacts directly with movement and positioning rules. Standard 5-foot-reach combatants are not threatened at 10 feet by each other.

Grapple interactions: A grappled creature that escapes a grapple and then moves may still trigger an opportunity attack, since escaping the grapple condition and moving are separate actions. See grappling rules for the full escape sequence.

Spellcasting and movement: A spellcaster who moves out of reach does trigger an opportunity attack. Casting a spell — including casting within reach — does not itself trigger an opportunity attack, because the trigger is movement, not the casting action.

Decision boundaries

The line between what triggers and what does not trigger an opportunity attack is governed by 4 explicit rule conditions:

• Disengage action: Using the Disengage action on a creature's turn causes all movement that turn to not trigger opportunity attacks. This is a full action cost, not a bonus action, unless a class feature (such as the Rogue's Cunning Action) allows Disengaging as a bonus action.
• Teleportation: Any movement that is teleportation — including the Misty Step spell, the Monk's Step of the Wind, or a Blink spell effect — does not trigger opportunity attacks, because the creature never physically passes through the threatened space.
• Forced movement: Being pushed, pulled, or thrown by a game effect (such as Thunderwave or a shove) does not trigger opportunity attacks on the moved creature. However, the D&D optional rules reference includes variant rules some tables adopt that modify this.
• Reach-exiting vs. within-reach movement: Movement entirely within a creature's reach does not trigger an opportunity attack. The trigger requires leaving the reach, not simply moving while inside it.

The Sentinel feat (published in the Player's Handbook by Wizards of the Coast) modifies standard opportunity attack behavior in 3 ways: it eliminates the speed reduction on hit targets, it allows opportunity attacks against creatures using the Disengage action, and it reduces a triggering creature's speed to 0 on a hit. These modifications make Sentinel one of the highest-impact feat choices for melee builds, directly reinforcing the tactical geometry covered in flanking rules and the broader strategic layer of how D&D works as a system.

References

• D&D 5th Edition Basic Rules — Combat Chapter, Wizards of the Coast
• D&D 5th Edition Systems Reference Document (SRD 5.1), Wizards of the Coast
• Player's Handbook, Wizards of the Coast — Feats (Sentinel), Chapter 6