The most stable element known is iron, or more specifically, an isotope of iron known as iron.
However, you may be perplexed and wonder what noble gases are, noble gases are the most stable elements in the periodic table, this is also true but to an extent.
Various stability criteria are commonly used, in other words, noble gases are chemically stable.
Iron-56 has both structure and atomic stability, It has the smallest average mass per nucleon.
On the other hand, noble gases have a lower binding energy per nucleon than iron.