Yes. Go to the Races window (CTRL + F2) and use the delete button at the bottom of the window. Make sure you have the correct race selected in the empire name! I have done that one myself....
So im trying to set up a multi start game with multiple player races. I realised that i had made come critical errors in one of the player races in my game and need to delete them and start again. Is there a way to do this?