  We obtain the first exact solution for the stationary one-dimensional
Kardar-Parisi-Zhang equation. A formula for the distribution of the height is
given in terms of a Fredholm determinant, which is valid for any finite time
$t$. The expression is explicit and compact enough so that it can be evaluated
numerically. Furthermore, by extending the same scheme, we find an exact
formula for the stationary two-point correlation function.
