The show's executive producers Julie Plec and Kevin Williamson previously revealed that they were searching through hundreds of audition tapes to find the right actor for the part.
TV Line claims that Morgan has now signed up to play the powerful, original vampire.
Morgan has appeared in a number of British shows such as Casualty, Doc Martin and Hex and he also starred in the movies Alexander and Master And Commander.
The Vampire Diaries airs on Thursdays at 8/7c on The CW. The second season returns in the UK on February 1 at 9pm on ITV2.