A cross-cultural myth.
In Greek and Egyptian mythology, the phoenix was a beautiful bird that lived alone in the Arabian desert for 500 years (or 1,461 years, depending on who you're asking. Ain't like anyone got to hang around long enough to check, right?) and then consumed itself in a fire, rising renewed from the ashes to start another long life.
The phoenix was associated with the sun gods of both cultures (Re in Egypt and Phoibos, or Apollo, in Greece). In Egypt, it was often depicted as a heron; in Western lit, it often resembles a peacock or eagle. It's also been associated with Hinduism's Garuda and the Chinese Feng-huang.
Unsurprisingly, the phoenix has come to symbolize things like immortality and the renewed vigor of life in spring.
Research from http://www.pantheon.org/articles/p/phoenix.html