Rutherfordium (Rf) is a synthetic chemical element with atomic number 104. It is named in honor of the physicist Ernest Rutherford who, among other things, discovered the element radon.

Rutherfordium is the first so-called superheavy element, a label given to all elements with atomic number greater than or equal to 104.

At 13 letters, rutherfordium is the longest of all element names, followed by praseodymium, protactinium and darmstadtium which all have 12 letters.