What's the word for someone who opposes a generally established opinion? [duplicate]

I'm looking for a noun to describe someone who's against something. For example:

He's one of those people who oppose the idea of...

I know you can simply say "He's against the idea of", but I was wondering if there was any noun that I could use in this particular scenario. I thought about simply using the word opponent but isn't it more suitable in perhaps a competitive game context?

Solution 1:

I think contrarian may fit in the context you describe:

a person who takes an opposing view, especially one who rejects the majority opinion, as in economic matters.

• He is a contrarian who frequently writes controversial opinion pieces.

(Dictionary.com)

From Etymonline contrarian:

Latin contrarius (adj.) also was used as a noun meaning "an opponent, an antagonist." In English history, contrariant (from French, from Medieval Latin contrariantem) was the name given to Thomas, Earl of Lancaster, and the barons who took part with him in the rebellion against Edward II, "because, on account of their great power, it was not expedient to call them rebels or traitors" [Century Dictionary].

Solution 2:

Depending on the context, you could use different options:

• generic: dissenting person, dissenter
• with political connotation: dissident