This is one of my favourites in the British Museum - I visit her every time I go there, which is at least once a year. She lives in the Wolfson Galleries, not far from the Molossian Dog. She looks young, but she's well over two thousand years old - an Etrusco-Latin bronze, half life size, thought to have been found at Nemi and cast during the third to first century BC. There's more information about her on the British Museum site, though she has a presence and grace that I think my photo captures better than the BM one.
Hat tip: Kieron McNulty, who was kind enough to answer my appeal on the Open University Student Association's Classics Forum, found the link for me.