One could argue that the main theme in Hamlet is the complexity of death.

It is the death of old King Hamlet, Hamlet's father, that triggers the main events of the play. Once Hamlet hears from his father's ghost that he was murdered by his brother Claudius, the Danish prince immediately vows to exact a brutal revenge. Claudius is a murderer, and for Hamlet, the only appropriate punishment is death.

But Hamlet being Hamlet, a brooding, introspective young man, he doesn't just rush off and run Claudius through with a sword. Instead, he spends an inordinate amount of time thinking about death, such as in the famous “To be, or not to be” soliloquy, where he contemplates whether or not he should take his own life. Hamlet realizes, as lesser mortals wouldn't, that death is a complicated business.

Hamlet's single-minded obsession with death and its complexities can also be observed in the graveyard scene, where he is surrounded on all sides by bones and dead bodies. Here we see the multifaceted, complex nature of death. It is both spiritual—as seen in the ghost of Hamlet's father—and physical, as in the shape of Yorick's skull.

Hamlet's verbal jousting with the gravedigger epitomizes the often flippant attitude that the young prince has towards death. The attitude displayed here is redolent of an earlier scene in the play where Hamlet indulges in a spot of tasteless wordplay over the state of Polonius's corpse.

Though somewhat unpleasant, Hamlet's attitude towards Polonius's death—for which he was responsible—is at least in keeping with his understanding of death's numerous complexities. As death is a complicated matter, it is entirely appropriate that it should call forth a variety of paradoxical responses from Hamlet, some deadly serious, some almost jovial.

When approaching the idea of theme in literature, one good question to ask is "beyond the plot/action, what is the work really about?" 

In regards to Shakespeare's Hamlet, the answer to this question, for me, comes down to the notion of the moral conundrum of justice (law) versus morality.

This is just one way to phrase a rather complex moral/ethical scenario that stands at the heart of this play.

The character Hamlet is faced with a very difficult situation. In order to do the "right thing" in terms of justice and honor, Hamlet must revenge his father's murder. This is clear. 

Yet, avenging his father's death means acting against his own mother. This is wrong as a moral act. One cannot, morally speaking, destroy one's mother (her life, her marriage, etc.) and still claim to be acting morally. This is also clear. 

Thus, Hamlet's dilemma - to be (just) or not to be (just); to be (moral) or not to be (moral); to revenge his dead father against his living mother or to forgive his living mother and thereby wrong his dead father, leaving his honor sullied and his murder unavenged. 

To be, or not to be, that is the question:
Whether 't is nobler in the mind to suffer
The slings and arrows of outrageous fortune,
Or to take arms against a sea of troubles,
And by opposing, end them?
(III.i.55-59)

Many readers like to view Hamlet as profoundly indecisive. While it is difficult to argue against that interpretation of his character, we should not under-estimate the scale of his two options, each being rather absolute in their implications vis a vis Hamlet's spiritual state.

He has a choice between two condemnations. He can be condemned by the codes of honor and justice or condemned by the codes of morality. 

Should we wonder that he is indecisive?

As we see the famous lines of Hamlet's soliloquy above, choosing action means that he will have to destroy his mother and, by extension, destroy himself. We can argue that Hamlet will have nothing left of himself morally and spiritually if he goes against his mother and her husband. 

"Critics who find the cause of Hamlet's delay in his internal meditations typically view the prince as a man of great moral integrity who is forced to commit an act that goes against his deepest principles" (eNotes). 

In any event, we can certainly argue that a central theme - perhaps the central theme of Hamlet is found in the conflicting sensibilities or codes of conduct represented by "justice" and "morality." 

There are many themes found in William Shakespeare's tragic play "Hamlet." The first theme found in the play is revenge. The theme of revenge is made apparent through the movement of the characters' actions. Many of the characters' actions are completed based upon one, singular idea: enacting revenge upon another. At the same time, the themes of death and fate are woven together with revenge. The themes play off of each other in order to highlight how revenge typically ends in death while speaking to the fate of the character at the same time.

That said, another theme (typical of the period) is the presiding power of good. Essentially, many of Shakespeare's plays (especially the tragedies) denote the importance of good overpowering evil. The idea that good is far more powerful is seen through the tragic death of the tragic hero (typically). With the death of the tragic hero, who possesses a tragic flaw, good can triumph.

What are the main themes in Hamlet?

Uncertainty: Hamlet wishes to avenge his father and punish both his mother and uncle, but he does not know the moral or proper way to achieve justice.

Fortune or Chance: Hamlet could not save his father. No matter how carefully he plots his revenge, chance events lay waste to his plans. In Act 3, Scene 1, Hamlet believes his uncle is hiding behind the curtains in his mother’s room. In fact, however, the person who is hiding is Polonius, Ophelia’s father. Hamlet kills him and sets off an unanticipated chain of events.

Mortality: Hamlet is grief-stricken by the loss of his father. When he comes upon Yorick’s skull, Hamlet realizes the permanency of death. He thinks of all the great men who have come before him and not a single one has escaped death.

“Alexander died, Alexander was buried, Alexander returneth / into dust; the dust is earth; of earth we make loam; / and why of that loam, whereto he was converted, might / they not stop a beer barrel? / Imperious Caesar, dead and turn'd to clay / Might stop a hole to keep the wind away”

What are some major plot points in Hamlet that convey the play’s most important themes?

The first significant plot point takes place in act 1, scene 5, when Hamlet interacts with his father's ghost, who informs him of Claudius's treachery. The ghost instructs Hamlet to avenge his death by killing Claudius but specifically tells him not to harm Gertrude. This important plot point sets the play in motion, as Hamlet becomes consumed with the idea of seeking revenge. This moment also underscores the theme of revenge, which runs throughout the entire play.

Another significant plot point concerns Hamlet's mad behavior, which upsets Ophelia and worries Claudius and Gertrude. Claudius hires Rosencrantz and Guildenstern to work for him and spies on Hamlet to discover the source of his madness. This plot point underscores the prominent themes of madness and deception.

Hamlet's production of the "The Mousetrap" is another significant plot point, where Hamlet confirms the ghost's message. Hamlet is initially motivated to kill Claudius once he discovers that his uncle did indeed assassinate his father. This plot point underscores the themes of guilt and sin, as Claudius cannot endure witnessing a reenactment of his horrible crime.

Another significant plot point takes place in act 3, scene 4, when Hamlet harshly criticizes Gertrude for her relationship with Claudius and brashly kills Polonius, who is spying on him from behind an arras. This plot point leads to Hamlet’s exile and eventual return. This scene also explores the themes of violence and deception.

Once Laertes returns to Denmark, he vows to avenge his father's death, and Claudius directs his attention to Hamlet. This plot point leads to the tragic fencing match between Hamlet and Laertes and highlights the themes of revenge, violence, and manipulation.

What are the major concerns/themes of Hamlet?

Since the play begins with a question and is full of philosophical questions, the two major concerns of Hamlet are:

Is man supposed to be an active agent or a passive suffering creature in the world?

Hamlet's famous "To be or not to be" monologue presents two opposing views: "suffer the slings and arrows of outrageous fortune" or "take arms against a sea of troubles"?

Hamlet is not given much of a choice by his father, the Ghost: revenge him and leave Gertrude "to heaven."  Hamlet knows he's not cut out to be an avenger, and most of his anger is not directed toward the males; rather, it's focused on his mother.  So, how can he summon up the courage to kill a heavily guarded king who may or may not be guilty?  It's an existential and profoundly moral dilemma.  Hamlet finally decides, "Let be...the readiness is all."  He says we must live ready to die.

What is the nature of death and the afterlife?

There's moral confusion in the play and with Hamlet himself.  The Ghost's appearance confirms a supernatural afterlife.  Hamlet must find a way to kill Claudius and send him to hell, but killing will also send Hamlet to his death and hell as well.  There's little chance Hamlet can carry out the Ghost's wishes and both save his life and guarantee his afterlife in heaven.

Also related is the nature of the heavenly father: how can Hamlet's father's Ghost (symbolic of the Old Testament Yahweh) condone revenge if he knows Hamlet is a Christian?  So, Hamlet becomes a Christ-figure, torn between the expectations of his vengeful heavenly father and his own beliefs in Christian forgiveness.

What are the major concerns/themes of Hamlet?

There are a number of important themes, obviously, and you can peruse them at your leisure at the rather thorough guide below.  But in brief:

Hamlet, the prince, is filled with self doubt and much of the play is centered around his attempts to resolve his own doubts and take action about the fact that he believes his father was murdered.  He spends a great deal of time thinking deeply (and telling us all about it) about the various issues, religious, moral, etc. surrounding his currend predicament.

Another major theme is that of deception and intrigue.  So much of what happens goes on behind the scenes or involves one character trying to trick or outfox another, or to even keep actions in the dark, that much of the play is about who can figure out what who else has done and how to counteract or explicate that action.

What are the major concerns/themes of Hamlet?

A play that is this famous surely has many themes and concerns.  I will discuss a couple of them.

First, you can say that it is a play about revenge and human motivation.  Many characters in the play (Hamlet, Laertes, Fortinbras) want to get revenge on someone.  We explore their reasons for wanting revenge.  We also see that Hamlet is much less motivated than the others and does not seek his revenge as forcefully.  Why is this?

Second, this is a play about how unavoidable death is and how it comes about both on purpose and by chance.  Polonius is killed by chance.  So is Gertrude.  Others are killed on purpose.  But everyone dies.

What is(are) the major theme(s) in William Shakespeare's Hamlet?

The major themes of Hamlet are almost too many and too varied to state succinctly. Some to consider are:

1. Revenge/Vengeance: Hamlet is revenging the murder of his father.
2. Death/Suicide: Hamlet considers killing himself, "To be or not to be"; Ophelia dies, the priest says by accidental, not by intentional, suicide:

   First Priest
   Her obsequies have been as far enlarged
   As we have warrantise: ...
   ... that great command o'ersways the order,
   [...]
   Yet here she is allow'd her virgin crants,

3. Confusion/Mystery: Frustration arises from the play because answers are elusive: Is the Ghost a demon? Is Hamlet crazy? Is Polonius good or bad? Does Hamlet love Ophelia? Did Ophelia kill herself?   
4. Love/Lust: Hamlet and Ophelia seem to love each other. Then she rejects his letters and he breaks her heart. Gertrude seems a loving Queen and mother. Then she remarries exceedingly quickly after King Hamlet's death.

As a side note about Ophelia's death, the Catholic Church made (and makes) an exception in the designation of suicide when the person was in "[g]rave psychological disturbances, anguish, or grave fear ...."

List and explain the main themes of Shakespeare's Hamlet.

Shakespeare's Hamlet contains numerous themes.  The play treats the issue of good vs. evil and the nature of evil.  Regicide contributes to this theme.  The justness of tyrannicide, Claudius's short-term guilt, the far-reaching effects of an evil act all contribute to this idea.

Death, of course, is everywhere in Hamlet.  Corpse-eating worms, skulls, suicide, death by sword, death by execution, death by poisoning all appear. 

Connected to death is rottenness, literal and figurative.  Rotten bodies are described, and something is rotten in the state of Denmark.

The theme of seeming, the difference between appearance and reality, is also present.  Is the ghost a ghost or a deceiving demon?  Hamlet seems sad over his father's death, says Gertrude, and Hamlet retorts that he doesn't seem sad, he is. 

Melancholy and madness, revenge, chance and happenstance, of course, are also some of the themes present in Hamlet.

What's the theme of Hamlet?

Like many of Shakespeare's plays, Hamlet can be read and interpreted on many different levels.  The most popular and common theme, however, seems to be the theme of revenge.  The audience sees this theme play out in the tragedy as Hamlet vows to avenge his father's death.  He becomes so consumed in his quest that he ends up destroying the relationships (and, in some cases, lives) of those he loves, while he also begins questioning death and his own mortality.  I would say this is also a central theme because everything else plays off of Hamlet's obsession with seeking revenge.   

What's the theme of Hamlet?

There is surely more than one theme to a play as complex as Hamlet is.

On one level, the play is about corruption, evil, and the need to take revenge.  We see this as Hamlet ends up killing all those he feels are responsible for the killing of his father.

On another level, this is a play about death and the futility of life.  You can see the idea of the futility of life in the famous "to be or not to be" soliloquy.  You can see the theme of death in the fact that essentially all the major characters die.

There are surely other themes that others would see in this complex play.

What is the theme of Hamlet?

Hamlet is a notoriously complicated play, full of subplots, and the title character's frequent musings on issues fundamental to the human condition themselves make it very difficult to reduce the play to a single theme. Some might argue that revenge, the central element to the plot, is the play's main theme. But a strong case could be made for death. From the appearance of King Hamlet's ghost to the play's bloody denouement in the duel between Hamlet and Laertes, death is literally everywhere in Hamlet. Moreover, death is addressed in different ways, particularly by Hamlet himself.

On the one hand, we find Hamlet pondering the spiritual aspects of death, wishing on the one hand that God had not outlawed suicide, and then observing that "what dreams may come/When we have shuffled off this mortal coil" are the only thing that makes life preferable to death. Later, however, we find him pondering the visceral, physical aspects of death, in his brief aside on the ways in which a beggar might go through the "guts of a king" and, most famously, in his speech on Yorick's skull:

Alas, poor Yorick! I knew him, Horatio: a fellow
of infinite jest, of most excellent fancy: he hath
borne me on his back a thousand times; and now,
how abhorred in my imagination it is!

Death comes to all of the play's major characters except Horatio, who himself expresses a wish to take his own life as he watches his friend Hamlet dying. Polonius, his son Laertes, and Ophelia all perish, as do Claudius, Gertrude, and Hamlet. Some of the characters deserve their fate, others clearly do not. Death in Hamlet makes no such distinctions. There are, of course many other themes in the play: madness, corruption, appearances and reality, sex, and man's aloneness in the universe are all prevalent. But death has as strong a claim as any to be judged the main theme of the play.

What is the theme of Hamlet?

To add to your previous list:

Ambition (Claudius, Hamlet, Polonius, Ophelia)

Family Relationships (Ophelia, Laertes, Polonius/ Hamlet, Gertrude, Claudius, King Hamlet)

Madness (Hamlet, Ophelia)

Appearances vs. Reality (Hamlet "acts" crazy; King Hamlet as the ghost, Claudius as innocent heir to throne, Gertrude as ally or innocent wife of a murderer, Rosencrantz and Guildenstern as friends to Hamlet)

What is the theme of Hamlet?

This question has been asked and answered several times.  Follow the link:  http://www.enotes.com/hamlet/group/search?q=theme

A short list:

Revenge - major theme - similar to Roman tragedies in which a principal character is driven by revenge.

Mortality - purpose in life (Hamlet's "to be or not to be" speech is the center of this.  Ophelia's suicide also figures in this theme.

Friendship - Hamlet & Laertes, Hamlet & Ophelia, Rosencrantz & Guildenstern, etc.