Who is Anakin Skywalker's father?
In Episode 1: The Phantom Menace, Anakin's mother, Shmi, said that he does not have a father, although it seemed to me that she doubted that.
Is there a canonical answer as to who Anakin's father is? If so, who?
Pursuant to the rule that the prequels do not exist, this question remains unanswered. Anakin has a father, we're just never introduced to him ;)
It will be revealed in a future movie that Luke travels back in time on the planet Roswellooine and becomes his own grandfather.
In addition, although Darth Plagueis did attempt to influence the midichlorians to create the ultimate Sith weapon alongside Darth Sidious, the experiment was ultimately a failure, and the midichlorians, sensing the Sith's inherent malevolent intention, not only refused to do so, but in retaliation, conceived Anakin Skywalker in order to destroy the Sith once and for all.
So, according to this, neither Darth Plagueis nor Darth Sidious are Anakin Skywalker's father, the midichlorians really conceived him without any outside direct intervention.
An article over at secrethistoryofstarwars (take this link with a pinch of salt I have no idea how "canon" it is), stating early writings of the ROTS script actually had Darth Plagueis "manipulating midichlorians " to create life, thus creating Anakin.