Unbiunium（Ubu）是一种尚未被发现的化学元素，它的暂定化学符号是「Ubu」，原子序数是121，在元素周期表中排列在第8周期。

An extended periodic table theorizes about elements beyond element 118 (beyond period 7, or row 7). Currently seven periods in the periodic table of chemical elements are known and proven, culminating with atomic number 118.

If further elements with higher atomic numbers than this are discovered, they will be placed in additional periods, laid out (as with the existing periods) to illustrate periodically recurring trends in the properties of the elements concerned. Any additional periods are expected to contain a larger number of elements than the seventh period, as they are calculated to have an additional so-called g-block, containing at least 18 elements with partially filled g-orbitals in each period.