**Fifty-nine** (59, LIX) is the natural number following fifty-eight and preceding sixty.

**Fifty-nine** is the 17th smallest prime number. The next is sixty-one, with which it comprises a twin prime.

**Fifty-nine** is also:

- The atomic number of praseodymium, a lanthanide.
- The number of icosahedra discussed in H. S. M. Coxeter, P. Du Val, H. T. Flather, and J. F. Petrie's book
*The Fifty-Nine Icosahedra*. - The designation of Interstate 59, a freeway that runs from Louisiana to Georgia.