Cate took the world by surprise with her unexpected look which is apparently due to a role.
According to her makeup artist Morag Ross, Cate's daring hair transformation is to help her look the part for her current role at the National Theatre.
Given that's the case, we reckon Cate is likely to return to her natural light strands the moment that role wraps.
Mind you, who's to say?
She does look incredible - so much so that you could be forgiven for thinking she was a natural brunette. Cate, who presented an award at the BAFTAs, could certainly keep her new look. We can't imagine anyone complaining!
We'll just have to wait and see.
In the meantime we can enjoy her looking utterly stunning in this new, surprisingly-flattering rich shade.