Fluorosulfonate, in organic chemistry, is a functional group that has the chemical formula F-SO₂-R, and typically is a very good leaving group. In organic chemistry, fluorosulfonate is different than fluorosulfate. In fluorosulfonates, sulfur atom is directly bonded to a non-oxygen atom such as carbon. In inorganic chemistry, fluorosulfonate is another term for fluorosulfate, the anion F-SO₂-O⁻, the conjugate base of fluorosulfonic acid. They form a series of salts with metal and organic cations called fluorosulfates.

Organic (alkyl) fluorosulfonates are usually strong alkylation agents, similar to triflate esters (F₃C-SO₂-OR). But unlike the triflate group, the fluorosulfonate group is not stable against hydrolysis. Therefore, fluorosulfonate esters are less frequently used as alkylation agents than triflate esters.