Severus Snape's Entire Backstory Explained

The Harry Potter books and movies are filled with unforgettable characters, from students like Hermione Granger and bullies like Draco Malfoy to professors like Minerva McGonagall and the villainous Lord Voldemort. However, of all of the characters in Harry Potter, few are as fascinating as Severus Snape, the Slytherin potions master who seems like one of the cruelest villains for nearly the entire series.

Played by the late, great Alan Rickman in the films, Snape is a mysterious and unforgiving figure who, as a professor, favors Slytherin students and discriminates against Gryffindors, especially Harry and his group of friends. However, if you've read the books or watched the films, you know there's much more to Severus Snape than meets the eye. From lifelong vendettas to his long-lost love and his true allegiance, here's the entire, fascinating backstory of Severus Snape, explained in full. 

Spoilers for the Harry Potter film & books to follow!

Born to Muggle Tobias Snape and witch Ellen Prince, young Severus Snape has a difficult childhood due to a strained and often angry relationship between his parents, which Harry personally witnesses when he accidentally glimpses one of Snape's private childhood memories. However, Snape's life takes a turn when he meets a young Lily Evans, who lives nearby. Quickly, the two become close friends, and Snape tells Lily, a Muggle-born witch, about Hogwarts and their future there together.

Despite Snape and Lily's bond, they still argue, especially when her sister, Petunia — Harry's bitter Muggle aunt — gets involved. Ultimately, the tension between Snape, Lily, and Petunia comes to a head when Petunia, jealous of Snape's and Lily's respective magical abilities, spies on the two friends. When Snape accidentally injures Petunia using magic, she calls Lily a "freak," while Lily reveals that she and Snape saw a letter that Petunia wrote, begging Hogwarts to accept her as a student. By then, the damage is done, and Lily and Petunia are divided forever, thanks partly to Snape.

Upon their shared arrival at Hogwarts, Lily is furious at Snape for sabotaging her relationship with her sister, and matters only get worse from there. At the Sorting Ceremony, Lily is sorted into Gryffindor, while Snape ends up in Slytherin, ensuring that the two friends are separated for their entire tenure at Hogwarts.

While Snape and Lily try to remain close despite their differences, Lily disapproves of Snape's friends — all of whom later become Death Eaters under Voldemort — while Snape can't stand James Potter, one of Gryffindor's most popular students, who's clearly carrying a torch for Lily. It's especially bad since James has a penchant for bullying Snape. Though Lily assures her friend that she can't stand James, an altercation with the young bully ends in nastiness when Snape calls Lily a "Mudblood," a horrible slur referring to Muggle-borns ... and it effectively ends their friendship forever. 

Though Snape begs for her forgiveness, particularly because Lily was defending him against James, he can't justify hurting Lily, and she gives up on him for good.

After Snape and Lily leave Hogwarts, the space between them only grows as Snape joins Voldemort, the Dark Lord, to help him overtake the wizarding world, while Lily joins the resistance fighters of the Order of the Phoenix. However, when Snape eavesdrops on Dumbledore's meeting with Sybill Trelawney, who prophecies Voldemort's fall at Harry's hands, he begs Dumbledore to save Lily, James, and Harry at any cost, promising anything in return — though this comes after Snape asks Voldemort to spare only Lily, disgusting Dumbledore.

No matter how hard Dumbledore tries, Voldemort slaughters Lily and James, leaving only Harry alive and Snape bereft. In the horrible aftermath, Dumbledore convinces Snape that the only way to show his love to Lily is to protect Harry, the only part of her that survives, and make sure that her death and her sacrifice to save Harry's life won't be in vain, especially when Voldemort resurfaces to attack Harry. Snape begs Dumbledore never to tell anybody that he's protecting Harry, and the heartbroken wizard agrees to the painful task.

During Harry's first year at Hogwarts, the young wizard immediately gets on Snape's bad side, which is likely in large part due to the fact that Harry looks strikingly like his father, James, whom Snape detested during school. On top of that, Snape finds Harry to be arrogant and mediocre, as well as a boy who breaks rules to gain fame and glory. But even so, he sticks to his promise and helps Harry survive a harrowing first year at Hogwarts.

As it turns out, the magical Sorcerer's Stone, which can make gold and create eternal life, is hidden deep within Hogwarts, and Snape is one of the several professors charged with protecting it. Though Harry, Ron, and Hermione are convinced that Snape is working with Voldemort to try to steal the stone, it turns out that Professor Quirrell, the Defense Against the Dark Arts teacher, is the one actually searching for the magical item as he's possessed by the weak, bodiless spirit of the Dark Lord. And, in fact, Snape is working against him to protect Harry. Though Dumbledore tells Harry that Snape protects him as a debt to James, he doesn't divulge anything further, and the enmity between Harry and Snape continues.

As Harry begins his third year at Hogwarts, he receives an alarming piece of information. Sirius Black, a wanted murderer accused of killing 13 wizards with a single curse, has escaped Azkaban — the wizarding prison — and is apparently hunting Harry. As Harry tries to grapple with this horrifying news, he also grows suspicious of Snape, who keeps providing a mysterious potion to Professor Lupin, that year's Defense Against the Dark Arts professor, every month.

When the year draws to a close, Harry and Sirius come face to face, flanked by Ron, Hermione, and Lupin, and a shocking realization comes to light. Though Harry believes that Sirius — James and Lily's best friend — sold them out to Voldemort, the truth is that Peter Pettigrew, who was friends with all three, actually betrayed James and Lily and worked for Voldemort. Though Snape is handed the truth about Sirius on a silver platter, his hatred of the wizard clouds his judgment, as Sirius was once his schoolyard rival. As a result, he refuses to help bring down Pettigrew and tries to arrest his old enemy.

However, Snape isn't a stick in the mud all the time. Even though Harry, Ron, and Hermione attack him so that he doesn't turn Sirius in, he shows up at the last minute and tries to protect our heroes when Lupin turns into a werewolf (hence the monthly potion) and attacks everybody there. Of course, when Sirius eventually escapes, Snape is livid, creating even more tension between him and Harry.

In Harry's fifth year, now that Voldemort has officially returned, it's more important than ever for "the Boy Who Lived" to protect himself against the Dark Lord, who's skilled in the art of legilimency (meaning that he can delve into Harry's thoughts at any time). To help Harry learn to defend his mind, Dumbledore asks Snape to teach Harry the art of occlumency, which guards your mind against invading forces. However, the lessons quickly go awry. When Harry has difficulty shutting off his emotions to practice occlumency, Snape doesn't help anything, and their tension hits a breaking point when Harry inadvertently invades Snape's mind and sees a memory of his father, James, cruelly bullying Snape for no reason.

Furious, Snape kicks Harry out of his office and refuses to continue teaching him, but in the end, when Harry is convinced that Voldemort has captured Sirius, Snape goes out of his way to check on Sirius and alert the Order of the Phoenix about Harry's vision. Snape, however, doesn't join the Order in this particular fight against Voldemort at the risk of exposing his cover as a double agent for Dumbledore. At the end of Harry's fourth year, after Voldemort officially returns, Snape returns to his former master at Dumbledore's orders.

During Harry's sixth year, the Boy Who Lived finds himself completely consumed by a few mysteries. For example, why is Draco Malfoy acting weirder than normal? And who is the mysterious previous owner of Harry's used potions textbook? It used to belong to someone who went by the nickname of "the Half-Blood Prince," and this mysterious student scribbled quite a few notes in the pages that help Harry unlock the secrets of some truly powerful potions.

Well, both roads ultimately lead to Snape. Despite Ron's and Hermione's doubts, Harry is correct that Voldemort himself has enlisted Draco with a task, though he doesn't know that task is until it's too late. Plus, Snape is the so-called Half-Blood Prince. In other words, he was the potions genius who's been helping Harry excel at the art of potion-making all year.

In the midst of all of this, Harry and Dumbledore work together constantly to understand Voldemort's life and uncover his secrets, but their mission comes to a screeching halt when they return to Hogwarts after a night away to find the school overtaken by Death Eaters ... including Draco, who's been tasked by Voldemort with killing the headmaster. However, when the young bully corners a weakened Dumbledore, it seems like the wisened wizard is able to convince his terrified student to spare his life. And that's when Snape shows up and does the job himself. Horrified, Harry tries to chase Snape, but he disappears with his fellow Death Eaters.

Rather than attending Hogwarts for his seventh and final year, Harry continues the work he started with Dumbledore and hunts down Voldemort's horcruxes, objects containing pieces of the Dark Lord's soul. However, what he doesn't know is that Snape is secretly helping him.

Now Voldemort's apparent right-hand man, Snape is named the new headmaster of Hogwarts, which puts him in the perfect position to silently help Harry with the aid of Dumbledore's moving portrait, painted after his death. With Dumbledore's help, Snape manages to hide the Sword of Gryffindor in a forest for Harry to find, enabling him to destroy horcruxes (because the sword is strengthened by basilisk venom) and keep track of Harry in general, quietly assisting him in his mission to weaken Voldemort enough to finally bring him down. While all of this is going on, Snape's master is seeking out the Elder Wand, the wizarding world's most powerful wand and one of the legendary Deathly Hallows, to make sure he's undefeatable when the time comes to face off against Harry once and for all.

Snape stays by Voldemort's side throughout the Battle of Hogwarts, which turns out to be a fatal mistake. After hours of slaughter, Voldemort comes to a realization. The Elder Wand, which he stole from Dumbledore's tomb, won't work for him because he isn't the true "master" of it. Because Snape killed Dumbledore, Voldemort believes the wand will obey Snape, so he must defeat his right-hand man. And before Snape can beg for his life, Voldemort uses his pet snake and horcrux, Nagini, to murder him.

Unbeknownst to both Voldemort and Snape, Harry, Ron, and Hermione have been hiding and watching the entire scene unfold, and when Voldemort leaves the room, Harry rushes forward to try to save Snape. In his dying moments, Snape asks Harry to look at him — clearly a reference to Lily, in that Harry's eyes resemble his mother's — and gives him a vial of memories. When Harry explores them, he learns everything he needs to know. Snape served as a double agent for his entire life to protect Harry. He also learns that Snape's doe Patronus, after Lily's own Patronus, appeared to Harry in the woods and guided him towards Gryffindor's sword. 

Plus, Snape was never the true master of the Elder Wand, due to the fact that Dumbledore, who was dying of a terrible curse, asked Snape to kill him when the time came. This way, Draco's soul would be spared. And finally, Harry learns that he is the final horcrux, as part of Voldemort's soul imprinted on him during childhood, and he must sacrifice himself to bring down Voldemort.

After giving his life to defeat Voldemort, Harry is able to return to the realm of the living and face Voldemort one last time, and as the true master of the Elder Wand, he brings the Dark Lord down for good. In the aftermath of the battle, Harry gets the chance to live out his life, get married, and have children, and his second youngest son, Albus Severus, carries on Snape's legacy, especially as Harry tells his son that he named him for two of the bravest men he'd ever met.

Ultimately, Albus Severus — as detailed in the Tony Award-winning play Harry Potter and the Cursed Child — is sorted into Slytherin just like one of this two namesakes, eventually becoming close friends with Scorpius Malfoy (Draco's son) and setting off on a time-bending adventure befitting his father and both of the men for whom he was named. Snape may have been a villain throughout his life, but Harry made sure to remember him as a hero.