Queen Gertrude is Hamlet's mother and the wife of her dead husband's brother, King Claudius.
Gertrude is most definitely a central figure in the play – Hamlet spends a whole lot of time dwelling on her incestuous marriage to Claudius – but her character is also pretty ambiguous. Was she having an affair with Claudius before the death of Old Hamlet? Does Gertrude know that Claudius killed her former husband? Why does she drink the poisoned wine her husband has prepared for her son? Does she know it's poisoned? Or, is she just really thirsty? Like so many other issues in Hamlet, Shakespeare leaves these questions unanswered. But, that doesn't mean we can't or shouldn't think about them anyway.
First things first. Was Gertrude stepping out with Claudius while Old Hamlet was still alive? The Ghost all but accuses her of adultery and incest when he calls her new husband, Claudius, "that incestuous and adulterate beast" (1.5.9). Okay, it seems clear Gertrude's guilty of adultery (cheating on one's spouse) right? Not so fast. In Shakespeare's day, "adulterate" could refer to any sexual sin (like incest), not just cheating. But, if you really want to argue that Gertrude's a big old cheater, be sure to check out the ghost's emphasis on the marriage "vow" he made to Gertrude (1.5.9).
Next question. Did Gertrude know her late husband was murdered by her new man? Again, we can argue either way. For those of you who want to say "No way!" you'll want to note that the Ghost never accuses Gertrude of murder in Act I, scene iv. Also, Gertrude seems pretty surprised when Hamlet accuses her of "kill[ing] a king and marry[ing] with his brother" (3.4.10). On the other hand, we could also argue that Gertrude is surprised because, well, she's been caught. Take your pick.
Finally, does Gertrude know she's chugging poisoned wine in the play's final act? You know the answer to this one, right? It can go either way. In Laurence Olivier's film adaptation of Hamlet, Gertrude drinks knowingly, presumably, to save her son from certain death. (Too bad we're talking about a revenge tragedy here – nobody but Horatio gets to live through the final bloodbath.) This reading makes Gertrude the self-sacrificing mother Hamlet has always wanted her to be, don't you think?
So, what's the point of all this ambiguity? If nothing else, it reminds us that Gertrude is a complex figure and that we shouldn't fall into the trap of merely buying into Hamlet's point of view, which paints her as morally "frail" (1.2.6).
Hamlet's obsession with his mother's sex life is constant throughout the play and this, to some extent, also colors the way the audience views Gertrude. Early on in the play, we learn that Gertrude's "o'erhasty" and incestuous marriage to Claudius has shaken up Hamlet's world, leaving him with a sense that the world is contaminated, like an "unweeded garden" that's "rank and gross in nature" (1.2.6). His disgust with Gertrude also seems to spread out to encompass all women, which is made evident when Hamlet insists "Frailty, thy name is woman!". According to some literary critics, Hamlet is more disturbed by Gertrude's sexuality than the news of his father's murder. Even though the ghost warns Hamlet "Taint not thy mind, nor let thy soul contrive / Against thy mother aught: leave her to heaven" (1.5.9), Hamlet just can't seem to leave his mother alone. In fact, the ghost returns at one point to remind Hamlet that he shouldn't be fixating on Gertrude (3.4.1). You can check out our discussions of "Sex" and "Family" for more on this.Gertrude Timeline