I will describe a holographic approach towards understanding effective field theories of open quantum systems. Using an AdS black hole as a thermal environment, we will capture the effective stochastic dynamics of a probe system. The techniques apply equally well to situations where the quantum system of interest is coupled to short-lived (Markovian), or long-lived (non-Markovian) environmental degrees of freedom. The primary input of the effective field theory are the real-time thermal correlators of the environment. I will explain how these correlation functions can be computed using a gravitational implementation of the Schwinger-Keldysh contour. In particular, they have an intriguing connection to 2d CFT data through Liouville conformal blocks that we will exploit. Using these results, I will describe general properties of thermal $n$-point functions of holographic CFTs, and implications for hydrodynamic effective field theories.