proud as a peacock

overly proud; vain. (*Also: as ~.) Mike's been strutting around proud as a peacock since he won that award. I sometimes think Elizabeth must spend all day admiring herself in a mirror. She's as vain as a peacock.

Having a very high opinion of oneself, filled with or showing excessive self-esteem. For example, She strutted about in her new outfit, proud as a peacock. This simile alludes to the male peacock, with its colorful tail that can be expanded like a fan, which has long symbolized vanity and pride. Chaucer used it in The Reeve's Tail: "As any peacock he was proud and gay." [1200s]