  One of the few cases of AdS/CFT where both sides of the duality are under
good control relates tensionless $k=1$ strings on AdS$_3$ to a two-dimensional
symmetric product CFT. Building on prior observations, we propose an exact
duality between string theory on a spacetime which is not asymptotically AdS
and a non-conformal field theory. The bulk theory is constructed as a marginal
deformation of the $k=1$ AdS$_3$ string while the spacetime dual is a single
trace $T\overline{T}$-deformed symmetric orbifold theory. As evidence for the
duality, we match the one-loop bulk and boundary torus partition functions.
This correspondence provides a framework to both learn about quantum gravity
beyond AdS and understand how to define physical observables in
$T\overline{T}$-deformed field theories.
