Kelium, also unofficially known as Killium, is a extremely radioactive and unstable element which can be found in large amounts in Venus' core, as well as in small amounts on Earth. It's symbol is Ke, with an atomic number of 176. A Kelium atom has 176 protons and 176 electrons, the highest amount on record. Kelium was also the first natural element (an element that occurs in nature) to be discovered since the discovery of Francium back in 1939, a gap of 77 years. The element has 2 known isotopes, 666Ki and 667Ki, making it the heaviest element on record.

The element was discovered on December 25, 2016 by physicist Matthew Kelium, from which the element derives its name. It was found in the remains of the melted uranium cores inside the Fukushima Daiichi Nuclear Power Plant, which was devastated by the Tohuku earthquake and tsunami in 2011. Each uranium rod was found to have approximately 1 milligram of Kelium.