Ruthenium (Ru) is a metallic chemical element with atomic number 44. There are several stable ruthenium isotopes but ¹⁰²Ru (44 protons, 58 neutrons) is the most abundant.

Ruthenium was discovered by German-Russia chemist Karl Ernst Claus, and the element's name comes the Latin name for Russia, Ruthenia

Ruthenium is used in electrical contacts and as a catalyst.