Exceptional form of D=11 supergravity

Eleven-dimensional supergravity reveals large exceptional symmetries upon reduction, in accordance with the U-duality groups of M theory, but their higher-dimensional geometric origin has remained a mystery. In this Letter, we show that D=11 supergravity can be extended to be fully covariant under the exceptional groups E(n(n)), n=6, 7, 8. Motivated by a similar formulation of double field theory we introduce an extended "exceptional spacetime." We illustrate the construction by giving the explicit E(6(6)) covariant form: the full D=11 supergravity, in a 5+6 splitting of coordinates but without truncation, embeds into an E(6(6)) covariant 5+27 dimensional theory. We argue that this covariant form likewise comprises type IIB supergravity.