Abstract FPSOs usually require refrigeration, for removal of condensates and/or water before export of produced gas, or for treatment of gas to be used on board as fuel gas. This paper describes on-board refrigeration using a new combination of different concepts, none of which individually are new, to deliver refrigeration for FPSOs with environmental, cost, space and weight advantages. Usually, FPSO owners specify a non-flammable refrigerant, and most current applications use R-134a refrigerant. However, R-134a is a hydrofluorocarbon with high global warming potential (GWP = 1300). These high-GWP refrigerants are being phased out under the 2016 Kigali amendment to the Montreal protocol, and are already banned for new applications in many European countries. Low-GWP alternatives to R-134a include hydrocarbons such as propane (GWP = 3), ammonia (GWP = 0), hydrofluoroolefines (HFOs) and CO2 (GWP = 1). HFOs are new synthetic refrigerants with GWP generally <150, but are flammable, though less flammable than propane. CO2 was widely used as a refrigerant up to the 1930s, particularly in marine applications, but was superseded by early synthetic refrigerants such as R-12 and R-22, which were then phased out in the 1990s after discovery of ozone depletion effects. CO2 is limited in air-cooled applications at high ambient temperature conditions such as tropical climates, due to the high-pressure side of the system becoming supercritical, leading to high operating pressure and low efficiency. However, FPSOs mainly operate in deep water, and even where surface water temperature is high, say +30 deg.C as in the tropics, cold water below +20 deg.C, can be found at depths of 100-200 m, even at the equator. Use of cold seawater via deep inlet risers is already used for some other FPSO applications, and if used for cooling in CO2 refrigeration systems, the system can operate at subcritical conditions, power becomes competitive and an optimised CO2 refrigeration system can have lower power, smaller footprint and lower weight, compared to a similar optimised R-134a refrigeration system. CO2 is now a viable refrigerant for FPSOs, with environmental, cost, weight and operational advantages over R-134a. Using CO2 as above is a new combination of known concepts, none of which individually are new, to achieve a new and better refrigeration outcome specifically for FPSOs. It is not a proprietary technology of any company.