Ever since she made the leap to Hollywood, Kate has managed to get the balance between English rose and glossy West Coast style just right – so we're a little stumped by this outfit.
Ms Beckinsale was spotted wandering the streets of Los Angeles in a frilly tunic teamed with what can only be described as a Victorian doll's bloomers.
The frou-frou combo was topped off with a pair of black pirate boots for a truly eccentric finish.
Perhaps it's a hint that she's keen to do a Jane Austen-style period drama?
What do you think of Kate's look? Leave a comment below and let us know!