* The story of Amleth, a legendary Danish prince who avenged his father's murder, which was first recorded in the 12th century by the Danish historian Saxo Grammaticus.
* The Elizabethan revenge tragedy, which was a popular genre in the late 16th and early 17th centuries. Revenge tragedies typically featured a protagonist who sought revenge for the murder of a loved one.
* The works of Seneca the Younger, a Roman Stoic philosopher and dramatist whose plays were known for their violence and moral dilemmas.
* The works of Thomas Kyd, an English playwright whose play The Spanish Tragedy (c. 1589) was a major influence on Hamlet. The Spanish Tragedy featured a protagonist who feigned madness in order to avenge his father's murder.
Shakespeare drew on these various sources to create Hamlet, which is considered one of the greatest tragedies ever written.