Opportunity attacks is a massive feature in D&D 5th edition, allowing creatures to strike at enemies who move away from them. However, what happens when a creature is blinded? Can they still make opportunity attacks?

Firstly, it's important to establish what being blinded means in the context of the game. From DndBeyond:

A blinded creature can't see and automatically fails any ability check that requires sight. Attack rolls against the creature have advantage, and the creature's attack rolls have disadvantage.

So, can a blinded creature make opportunity attacks? The answer is no, they can't. Opportunity attacks are triggered by an enemy leaving the creature's reach, but it specifically says that a creature automatically fails any check that requires sight.

Not to mention that you'd have disadvantage on the attack roll in any case, so it's best not to even try.