“I will show [you] what a woman can do,” declared Artemisia Gentileschi. And she certainly did, defying all societal expectations to become a pivotal 17th-century figure. Artemisia challenged established norms, whisking women out from under the male gaze and portraying their power. This exhibition, the first major Artemisia retrospective in the U.K., features her best-known paintings—including not one but two versions of Judith ferociously beheading Holofernes—as well as self-portraits and personal letters. —E.C.