No he wasn't.

As a quick aside Darwin didn't come up with the Theory of Evolution. He came up with Natural Selection, a mechanism to explain how evolution worked. This was because ideas regarding evolution already existed and had been discussed for quite a time.

Before Darwin there was Jean-Baptise Lamarck. Much of his work was discredited, both in his own time and then especially after Darwin, even though today it has made a little bit of a comeback.

In 1801 Lamarck wrote:

. . . time and favorable conditions are the two principal means which nature has employed in giving existence to all her productions. We know that for her time has no limit, and that consequently she always has it at her disposal.

Lamarck basically thought that organisms would acquire traits in their lifetime through either using or not using the traits that they already had, either strengthening them or weakening them.

Erasmus Darwin, the grandfather of Charles Darwin, himself came up with something very similar to Lamarck's ideas on evolution even though it seems that both he and Lamarck had no idea of each other's work.

http://www.ucmp.berkeley.edu/history/lamarck.html

And that's just in modern times. Possibly the first person to discuss evolution was Anaximander (ca. 611 - 546 B. C. E.). It's not known what he wrote as his work only survives in the writings of others, but he seems to have believed that there were no humans in the beginning and that we came from fish (we now know that our early ancestors were early fish). It's not known how he came up with this.

http://www.ucmp.berkeley.edu/history/ancient.html

So, Charles Darwin wasn't the first person to come up with evolution, it had been discussed for thousands of years prior to his work, and on top of that he wasn't even the first person in his family to work on it.

Edit:

I've read some books by Richard Dawkins in which he has discussed the history of evolution, unfortunately I can't remember which ones discussed the history of it but they backed up the above. It may have been The Greatest Show on Earth.