The Beating Heart Bride, whose name in life is often believed to have been Emily, possibly Emily de Claire or some variation of Emily Cavanaugh Gracey, was a human woman who is now a ghost.
Until the mid-2000's (when it was instead taken over by a very different ghost bride), the cluttered and cobwebby Attic of the Haunted Mansion was haunted by the wistful ghost of a lonely bride with shining yellow eyes and a darkened face, holding up a candle, whose heart glowed red in her chest, its echoing heartbeat filling the room.
Many conflicting tales are told about the Bride's origin, and as her appearance varied greatly over the years, it is sometimes reckoned that several similar ghostly brides haunted the attic in succession. At any rate, it is generally understood that the original Bride first glimpsed in the 1960's, with her darkened skeletal face, was the bride-to-be of the Hatbox Ghost.
Behind the scenes
The Beating Heart Bride was first seen in 1969 in the Disneyland ride The Haunted Mansion.