yeah, right

yeah, right

I don't believe you; that's not true. A: "I once caught a fish that was longer than you are tall! I, uh, just didn't have the heart to kill such a majestic creature." B: "Yeah, right, Bill. Whatever you say." A: "Sarah said she was going to clean her room this weekend." B: "Ha, yeah, right! I'll believe it when I see it."
See also: right
Farlex Dictionary of Idioms.

Yeah, right!

exclam. the ultimate sarcastic response of disbelief. Yeah, right! You were just going through my desk looking for a pencil.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • (yeah,) sure
  • yeah
  • Yeah, right!
  • lose (one's) heart to (someone)
  • lose heart to
  • lose one's hear to
  • lose your heart
  • tall drink
  • tall timbers
  • timber