Source One: Saxo Grammaticus's Historica Danica (1200)

This historical source relates the story of a prince, Amleth, who avenges his father's murder, but things don't work for the young prince.  Grammaticus writes of the harsh, violent world of
Viking warlords, yet it does lend some credibility to the basic dilemma of Hamlet.  This story was widely circulated centuries before Shakespeare picked up a pen.

Source Two: Francois de Belleforest's Histoires Tragiques

For the first time, the tragic story of the Danish prince was given literary life when Belleforest took the historical account found in Grammaticus's text and published it in a collection of short stories.

Source Three: Ur-Hamlet (Thomas Kyd?)

Both of the earlier texts contained some crucial elements of the play (the hero's love interest, fratricide, feigned madness, adultery, spies, and revenge) only Ur-Hamlet, probably written by
Shakespeare's mentor Kyd, includes a ghost who craves revenge.  In fact, Kyd's other play, The Spanish Tragedy, includes some other elements that may have been incorporated into Hamlet:  a procrastinating protagonist who berates himself for talking instead of acting and who dies as he achieves his revenge; a play within the play; a heroine whose love is opposed by her
family, and another woman who becomes and commits suicide (Boyce 238-239).  If Kyd did not pen Ur-Hamlet, he and Shakespeare clearly shared access to the same source.

 

There are other sources, historical and fictional, that Shakespeare may have utilized, including women who killed themselves for love, (1577) and a barber who confessed (in 1538) to
murdering an Italian duke by putting lotion in his ears.  In this instance, Gonzago was the name of the murderer, not the victim, as in Shakespeare's play-within-the-play, "Mousetrap".