Kryptonite was a chemical element listed on the Table of Elements. It was a member of the Hypersonic series. (TNG: "Rascals")

The element Kryptonite had the symbol "Kr" which is the same atomic symbol used for Krypton. It is named after the fictional element from stories of Superman published by DC Comics. The DC version of Kryptonite is number 126 on the table of elements (a position in reality held by an as-yet undiscovered element provisionally named Unbihexium, Ubh).