Roentgenium is a highly radioactive metal located on the seventh period and eleventh group on the periodic table of elements. Roentgenium's longest lived isotope, Roentgenium 282, has a half-life of 120 seconds. However, a theoretical isotope of Roentgenium, Roentgenium 286 might have a half-life of 10.7 minutes. It was named after Wilhelm Roentgen, the man who discovered X-rays. It is expected to behave like a heavier analogue of gold. Roentgenium was discovered in 1994 by the GSI.

Due to its extreme half-life, Roentgenium does not have many uses outside of research.