A new long‐term research initiative in ocean acoustic signal processing has been announced by the Ocean Acoustic Program (Code 11250A) and the Mathematical Sciences Division (Code 1111) of the Office of Naval Research. Ocean acoustic signal processing is defined as the development of phase coherent signal processing formalisms that incorporate the physics of acoustic wave‐field propagation through and scatter from an anisotropic, inhomogeneous stochastic ocean environment. It is motivated by the problems of detection, classification, and source localization in both passive and active sonar systems.The Ocean Acoustic Program and the Mathematical Sciences Division invite the submission of 2‐ or 3‐page planning letters that outline research. The planning letters should include budget estimates for 1‐ to 3‐year research programs that address the key issues given above.