Reduction of the bulky 8-annulene thorium complex [Th{COT(TBS)(2)}(2)] (COT(TBS)(2) = eta-C8H6(tBuMe(2)-Si)(2)-1,4) by potassium yields the anionic compound {Th[COT(TBS)(2)](2)}K .(DME)(2), which was crystallographically characterized and is the first sandwich complex of Th(III). EPR spectroscopy indicates that the molecule possesses a 6d(1) ground state. A structural comparison is made with the isostructural uranium(III) complex and the thorium(IV) parent compound.