The conformational landscape of the bis(fluorosulfonyl)amide, [FSI](-), anion was analyzed using data obtained from Raman spectroscopy, molecular dynamics (MD), and ab initio studies. The plotting of three-dimensional potential energy surfaces and the corresponding MD simulation conformer-population histograms show the existence of two stable isomers, C-2 (trans) and C-1 (cis) conformers, and confirm the nature of the anion as a flexible molecule capable of interconversion between conformers in the liquid state. In ionic liquids, the two [FSI](-) conformers coexist in equilibrium, a result confirmed by the Raman data. The implications of the conformational behavior of the ion [FSI](-) are discussed in terms of the solvation properties of the corresponding ionic liquids.