1. Roger Delgado: The first incarnation of the Master to be identified as such beginning in "Terror of the Autons". He was a sparring partner of the Third Doctor.
2. Peter Pratt: Played a desiccated form of the Master in the 1976 story "The Deadly Assassin".
3. Geoffrey Beevers: Briefly played a desiccated form of the Master before taking over the body of Tremas in "The Keeper of Traken". Also frequently played the Master in Big Finish audio dramas.
4. Anthony Ainley: Having taken over Tremas' body, was the Master through the 1980s.
5. Gordon Tipple: Briefly played the Master in the 1996 "Doctor Who" TV movie, just before being executed by the Daleks.
6. Eric Roberts: Even in death the Master was dangerous, as his soul took over a man named Bruce in 1999 San Fransisco and menaced the Eighth Doctor, also in the TV movie.
7. Derek Jacobi: Played the "Professor Yana" incarnation, who had transformed himself into a human, removed his memories and hid at the very end of time in "Utopia". Jacobi also played the Master in the 2003 animated webcast "Scream of the Shalka" (webcast).
10. Michelle Gomez: The "Missy" incarnation ("Deep Breath" onwards), who had regenerated into a Time Lady and became an arch-nemesis of the Twelfth Doctor.
11. Alex Macqueen: Only played the Master in audio dramas.
12. David Garfield: Played the villainous "Professor Stream" in "The Hollows of Time" (audio story). Stream was supposed to be revealed to be the Master, but his identity was left ambiguous due to Big Finish not having the rights to the character at the time.
According to some sources, notably novelisations such as "Doctor Who and the Terror of the Autons" (novelisation of "Terror of the Autons") and "Doctor Who And The Doomsday Weapon" (novelisation of "Colony in Space"), the Monk (played by Peter Butterworth in "The Time Meddler" & "The Daleks' Master Plan") and/or the War Chief (played by Edward Brayshaw in "The War Games") are earlier appearances of the Time Lord later known as the Master. However, other sources, such as "Timewyrm: Exodus" (novel), "No Future" (novel) and "The Dark Path" (novel), refute this. For more information, see Are the Master and the Monk and the War Chief the same person?