Hydrofluoroolefins (HFOs) and hydrochlorofluoro–olefins (HCFOs) are unsaturated short-chain haloolefins, which have been introduced as alternatives to saturated hydrofluorocarbons (HFCs) as refrigerants, due to their ultra-low GWP (Global Warming Potential).

Some products from both categories are listed in the Annex 2 of the EU F Gas Regulation 517/2014, which requires reporting but does not set any restrictions for use.