  We propose a stochastic modification of the Schr\"{o}dinger-Newton equation
which takes into account the effect of extrinsic spacetime fluctuations. We use
this equation to demonstrate gravitationally induced decoherence of two
gaussian wave-packets, and obtain a decoherence criterion similar to those
obtained in the earlier literature in the context of effects of gravity on the
Schr\"{o}dinger equation.
