The third benefit of the Sentinel feat is described as follows (PHB, p. 169):
- When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn’t have this feat), you can use your reaction to make a melee weapon attack against the attacking creature.
Does the third benefit of Sentinel count as an opportunity attack for the purpose of reducing their speed to 0 (per the first benefit of the feat)?
For reference, the description of the first benefit of Sentinel says:
- When you hit a creature with an opportunity attack, the creature's speed becomes 0 for the rest of the turn.
Best Answer
No, it's not an opportunity attack.
An opportunity attack is a specifically named game mechanic with specific rules set out for it (as found on page 195 of the PHB).
If the third benefit of the Sentinel feat was meant to be an opportunity attack, it would say something like:
As it's written, it's not counted as an opportunity attack because it doesn't say it is. What the third benefit of the Sentinel feat (PHB, p. 169) does say is that: