From The Art and Popular Culture Encyclopedia
The actor playing the title role is not always the lead; the title role may or may not be the protagonist. In the television miniseries Shogun, for example, Toshiro Mifune had the title role, but the lead was played by Richard Chamberlain. It can be even more complicated when the title role and the lead are in different genders; for example, in the recent revival of August Wilson's Ma Rainey's Black Bottom, Whoopi Goldberg, a film star, had the title role, but the lead was Charles S. Dutton.
The title character in fiction is the character whose name is contained in the title, as in Marjorie Morningstar, by Herman Wouk, The Adventures of Huckleberry Finn, by Mark Twain, and Dracula, by Bram Stoker. A more indirect example is Sauron in The Lord of the Rings by J. R. R. Tolkien.
Title characters are distinguished from real people, living or dead, since a character is a construct of fiction. For example, US President John F. Kennedy is not the title character of a biography entitled John F. Kennedy, since he was a real person.
A title character may not actually be named in the title. Instead, he or she is described, as in The French Lieutenant's Woman. Another example is An Ideal Husband by Oscar Wilde, where the 'ideal husband' (the title role) may be the apparently-perfect Sir Robert Chiltern, or it may be the enigmatic Lord Goring, supposedly a confirmed bachelor. Wilde's deliberately ambiguous title creates dramatic irony in this case, since it is difficult to say which of the acting co-leads has the title role.
Like title roles in film and theater, the title character need not be the protagonist. In The Lord of the Rings, for instance, Sauron, the title character, is the primary antagonist; in Stranger in a Strange Land by Robert A. Heinlein, the title character is Valentine Michael Smith but the character accepted as being the main character in that novel is Jubal Harshaw.