Abstract: A subsea multiphase fluid separation system and method are disclosed which provide for efficient and reliable remote separation operation at deep and ultra deep water depths including depths of ten thousand feet or more. The system is preferably of modular construction wherein the modules are secured in a single frame to be lowered as a unit to the seabed. The system utilizes reliable cyclonic operation. The sequence of process steps is designed to make the system more efficient as compared to surface separating systems and thereby permit a more compact size as is desirable for subsea operation. The method of operation includes up to five basic process steps with the initial step in one embodiment including cyclonically separating solids. In a presently preferred embodiment, the cyclonic solids separator is sized to eliminate solids greater than fifty microns. A second stage is directed to cyclonically removing bulk gas from the liquid in either a cyclone or auger separator.