Opportunity Attacks 5e: The Rule Everyone Forgets Mid-Combat

Opportunity attacks 5e are one of the shortest rules in the Player's Handbook and one of the most reliably skipped at the table. The trigger is a single sentence. The reaction cost is clean. And somehow, three rounds into most fights, a goblin darts past two melee characters, nobody swings, and everybody just keeps talking like that was normal.

It wasn't a house rule. Nobody decided reach doesn't matter tonight. The free attack just got lost in the noise of tracking initiative, HP, conditions, and whatever the bard is roleplaying this round.

That is the real problem with opportunity attacks 5e. The rule itself is not hard. What is hard is remembering it exists in the middle of a chaotic round, for every creature, every time reach actually gets crossed. StoryRoll testing across dozens of AI-run encounters keeps landing on the same conclusion: this rule doesn't fail because players misunderstand it. It fails because nobody is watching for the trigger.

Opportunity Attacks 5e: The Actual Trigger

Here is the whole rule, stripped down.

You can make an opportunity attack when a hostile creature that you can see moves out of your reach. That movement can come from the creature's action, its bonus action, its reaction, or any of its speeds. The opportunity attack itself uses your reaction, and it happens right before the creature leaves the space where you could still hit it.

That's it. No roll to see if you notice. No initiative check to react in time. If a creature you can see walks, runs, or is pushed by its own movement out of your reach, you get a free melee attack with a weapon you're holding or an unarmed strike.

Reach matters more than people think here. Most characters threaten a five-foot reach, meaning a creature has to move from a space within five feet of you to a space more than five feet away before opportunity attacks 5e even come into play. If you're wielding a reach weapon like a glaive or halberd, that threshold moves out to ten feet, and a lot of tables forget to extend it. A goblin that thinks it's dancing safely around a five-foot bubble can walk straight into a polearm's range and eat a free hit anyway.

What Opportunity Attacks 5e Do Not Punish

Half the confusion around this rule comes from the exceptions, and most groups only remember one of them.

Disengage stops it entirely. If a creature takes the Disengage action, its movement doesn't provoke opportunity attacks for the rest of that turn. This is the one exception everyone knows, mostly because it costs an entire action to buy that safety. A rogue who Disengages before running past three enemies is trading their whole turn's action for guaranteed safe movement, which is a real cost worth weighing, not a shortcut.

Forced movement doesn't count. If a creature gets pushed, pulled, or knocked around by something like Thunderwave, the Shove action, or a giant's slam attack, that movement doesn't provoke opportunity attacks 5e, because the creature isn't using its own action, bonus action, reaction, or speed to move. This one trips people up constantly in the other direction too. Players sometimes assume a shoved enemy is safe from everything nearby, when really the enemy simply didn't provoke anything from that particular push.

Teleportation is exempt. Misty Step, Dimension Door, and similar effects skip the whole question because the creature never actually crosses through the threatened space. No movement through reach, no trigger.

Extra Attack doesn't apply. An opportunity attack is a single melee attack, full stop. A fighter with three attacks on their turn still only gets one swing when they use their reaction for an opportunity attack, because the reaction only grants that one attack, not the whole Attack action sequence.

Why Tables Keep Forgetting Opportunity Attacks 5e Mid-Fight

This is the part rulebooks don't cover, because it isn't a rules problem. It's an attention problem.

A person running combat is tracking initiative order, HP totals for every creature on the field, active conditions, concentration, and whatever narration is happening on top of all of it. Opportunity attacks 5e require something none of that other bookkeeping does: watching movement in real time, for every character at the table, and catching the exact moment reach gets crossed. That's a lot to hold in your head while also deciding what the ogre says before it swings.

In practice, three things cause the miss over and over:

• The person running combat is narrating instead of tracking. If attention is on describing the hallway or reacting to a clever plan, the rogue slipping past the guard doesn't register as a trigger event. It just looks like movement.
• Reach gets estimated instead of measured. Theater-of-the-mind tables especially lose track of exact distance, so "did that creature actually leave 5 feet of reach" turns into a vibe check instead of a real answer.
• Players don't realize they have the option. New players in particular don't think to ask "can I hit them as they run past," because nothing in the fiction prompts the question. The rule is reactive by design, and reactive rules get skipped when nobody's watching for the cue.

None of that means the table is playing badly. It means opportunity attacks 5e are a rule that depends on consistent tracking, and consistent tracking is exactly the kind of thing that degrades under normal table chaos. The rule doesn't get harder as a fight goes on. The attention required to catch it does.

The Feats That Change the Opportunity Attacks 5e Math

A few character options rewrite this rule enough that it's worth knowing them before they show up at your table.

Sentinel is the big one. It lets you make an opportunity attack when a creature within your reach attacks someone other than you, even if that creature never moved. It also stops a creature's speed entirely if you hit it with an opportunity attack, and it lets you make an opportunity attack even against a creature that Disengaged. That last part matters because it's the one clean counter to the Disengage exception described above: a Sentinel character effectively removes that escape option for anyone standing in their reach.

War Caster lets you replace an opportunity attack with a spell instead, as long as the spell has a casting time of one action and targets only that creature. A Cleric or Paladin holding Shocking Grasp or Hold Person in reserve turns a routine opportunity attack into something a lot more disruptive.

Mage Slayer, Polearm Master, and reach weapons all shift the geometry rather than the trigger itself, extending or adding opportunity attack chances rather than changing when the rule applies.

None of these need to be memorized to run a normal session. They matter because a single Sentinel character at the table changes how every other creature has to think about movement, and forgetting that a PC or monster has it is its own version of the same mid-combat memory problem.

Where an AI Game Master Actually Helps With Opportunity Attacks 5e

This is exactly the kind of rule StoryRoll is built to hold onto, because it's a state-tracking problem more than a knowledge problem. The system knows where every creature is relative to every other creature's reach, so when a goblin's movement would cross that line, the opportunity attack gets offered instead of quietly skipped because the room got loud.

That doesn't remove the decision from the player. A readied Sentinel character still chooses whether to use a reaction that round, same as always. What changes is that the trigger doesn't slip through because someone was mid-sentence describing torchlight on stone walls. The rule fires when the fiction says it should fire, every time, which is the part human attention has the hardest time doing consistently across a three-hour session.

If you've ever ended a fight and realized halfway through the next one that the party had been walking past armed guards for free the whole night, that's not a rules failure. That's the exact gap this kind of tracking is meant to close.

Frequently Asked Questions

What triggers an opportunity attack in 5e?

An opportunity attack in 5e triggers when a hostile creature you can see moves out of your reach using its action, bonus action, reaction, or one of its speeds. You get one melee attack with your reaction, made right before the creature leaves your reach.

Does the Disengage action stop opportunity attacks 5e?

Yes. Taking the Disengage action means your movement does not provoke opportunity attacks for the rest of that turn. It costs your action, which is the trade-off most players forget to weigh.

Do opportunity attacks 5e use your action or your reaction?

Opportunity attacks 5e use your reaction, not your action. That means you only get one per round unless a feature like Sentinel or War Caster changes that, and you can't also use your reaction for something else, like a Shield spell, in the same round.

Does forced movement trigger opportunity attacks 5e?

No. Forced movement from effects like Thunderwave or the Shove action does not provoke opportunity attacks, because the creature isn't using its own action, bonus action, reaction, or speed to move. Teleporting, such as with Misty Step, doesn't provoke one either.

Does Extra Attack apply to opportunity attacks 5e?

No. An opportunity attack is a single melee attack made with your reaction, and it does not benefit from Extra Attack or any other feature that grants additional attacks on your turn.

If you want to see how the rest of 5e combat holds up under the same kind of scrutiny, cover rules, flanking, the Ready action, and initiative all have the same pattern: clean rules on paper, constant slippage at a live table.