  The Celestial Holography program encompasses recent efforts to understand the
flat space hologram in terms of a CFT living on the celestial sphere. A key
development instigating these efforts came from understanding how soft limits
of scattering encode infinite dimensional symmetry enhancements corresponding
to the asymptotic symmetry group of the bulk spacetime. Historically, the
construction of the bulk-boundary dual pair has followed bottom up approach
matching symmetries on both sides. Recently, however, there has been exciting
progress in formulating top down descriptions using insights from twisted
holography. This chapter reviews salient aspects of the celestial construction,
the status of the dictionary, and active research directions. This is a
preprint version of a chapter prepared for the Encyclopedia of Mathematical
Physics 2nd edition.
