The Victorian poet Elizabeth Barrett Browning suffered for most of her life from an illness that her physicians were never able to diagnose, and that Barrett Browning scholars and others have tried to diagnose since her death in 1861. Many suggestions have been offered, but none has been convincing. By happenstance, my daughter was reading the correspondence of Elizabeth and Robert Browning not long ago, and she recognized the symptoms described as those of the rare muscle-weakening disorder she herself has, hypokalemic periodic paralysis (HKPP). The evidence from Barrett Browning's letters and the diary she kept when she was 25 strongly suggest she too had HKPP.