Paul McGann played the Doctor in the BBC-Fox Broadcasting Company continuation of the television series. In the event, only one television episode ("Doctor Who", the TV Movie) was made but, in it, the Seventh Doctor (played by Sylvester McCoy, as in the classic series) regenerated into McGann's Eighth Doctor.
Following this, the Eighth Doctor, as played by McGann, appeared in his own run of BBC Eighth Doctor Adventures novels, in the BBC's "Shada" (webcast), in a large number of Big Finish audio stories and in many other stories in various media.
He has also been referenced several times in the New Series (in "Human Nature"/"The Family of Blood", "The Next Doctor", "The Name of the Doctor" & "The Day of the Doctor", for example) and was seen in his own mini-episode, "The Night of the Doctor", in which he regenerated into the War Doctor (played by John Hurt).
Finally, official BBC publications consistently name him as the Eighth Doctor.