It could be to a close friend or confidant, someone he trusts to listen and understand.
It's possible that Montresor is telling his story to a priest or a confessor, seeking some form of absolution or validation. Another possibility is that he's sharing it with an audience of strangers, simply needing to get it off his chest.
Maybe he's telling it to a fellow revenge-seeker, someone who can relate to his motives and actions. Or it could be to a neutral party, like a historian or a chronicler, just to have his tale recorded.
One possibility is that he could be telling his story to a priest. In the context of seeking absolution, Montresor might be confessing his dark deed. Priests are often the recipients of confessions, and Montresor, burdened by his conscience perhaps, could be unburdening himself to a man of God.
Montresor is telling this story to an unnamed person. We don't get a clear identification of who this person is in the story. It could be someone he trusts, or perhaps he's just unburdening his conscience to a random listener.
The recipient of Montresor's tale is ambiguous. It might be someone he considers a confidant, or it could be a symbolic act of sharing his burden with an imagined audience to unburden his conscience.
He could be confessing to a close friend. Someone who he believes will understand his motives, or at least keep his secret. A friend who has known him for a long time might be more likely to accept his confession without immediately judging him harshly.
Well, it could be someone close to him, like a confidant or a friend.
He could be confessing to a priest. In many literary works, a character might confess their sins to a religious figure. Montresor's act was a heinous crime, and confessing to a priest would be a traditional way to seek absolution, though there's no clear indication in the story that it's a priest.
Maybe he wants to get something off his chest or seek some kind of validation.
There's no clear indication in the text about who Montresor is telling the story to. It leaves it up to the reader's imagination.
It could be to the reader. Often, narrators in novels or short stories are implicitly addressing the reader, sharing their tale as if we are the confidants.
Odysseus is telling his story to the Phaeacians. They are a kind and hospitable people who offer him shelter and listen to his long and arduous journey.