Fursultiamine (INN; chemical name thiamine tetrahydrofurfuryl disulfide or TTFD; brand names Adventan, Alinamin-F, Benlipoid, Bevitol Lipophil, Judolor, Lipothiamine) is a medication and vitamin used to treat thiamine deficiency. Chemically, it is a tetrahydrofurfuryl disulfide derivative of thiamine and is similar in structure to allithiamine.

It was synthesized in Japan in the 1960s from allithiamine for the purpose of developing forms of thiamine with improved lipophilicity for treating vitamin B₁ deficiency (i.e., beriberi), It was subsequently commercialized not only in Japan but also in Spain, Austria, Germany, and the United States.