In the perdurable Harry Potter franchise, the majority of wizards and witches in the Wizarding World are not actually able to create their own individual Patronuses. As a result, the magical charm contains a certain degree of mystery to its formation. Even though the most gifted witches and wizards tend to struggle with producing a Patronus, Severus Snape — who was interestingly half-blood — was able to produce his own Patronus, which is a Doe.
Before we can examine why Snape’s Patronus is a Doe, we first have to thoroughly explain what exactly a Patronus is. According to the Wizarding World, a Patronus is produced through “memories of happiness and hope.” Additionally, Patronuses represent a deeply-rooted love, and the influential power of happy memories. It is a protection charm that is affected by a person’s positive feelings, and thus, when they are at their happiest.
So, why is Snape’s Patronus a doe?
Snape’s Patronus is a Doe because of his outstanding love for Lily Evans, the mother of Harry Potter. Snape met Lily when they were children and immediately developed a crush on her. However, Lily also harbored intense feelings for James Potter, and ultimately, she fell in love with James over Snape. Because Snape’s feelings for Lily were so extreme, and because people typically take on the Patronus of the one they love the most, Snape’s Patronus is a doe. Moreover, Snape’s happiest moments were during time he spent with Lily, thus his Patronus took the same form as hers.
As revealed in the Deathly Hallows, Snape served as a double agent for both Dumbledore and Voldemort, secretly forming a plan with Dumbledore to gain Voldemort’s trust in an attempt to understand his agenda. Snape performed such a brave act in order to protect Harry Potter for the sole reason of his love and dedication to Lily. In the Deathly Hallows, Harry is specifically led to the sword of Gryffindor by a doe, which is revealed to be Severus Snape’s Patronus.
When Harry discovers Snape’s memories with Dumbledore, Snape reveals his Patronus to Dumbledore. Dumbledore is immediately surprised, to which it is revealed that Snape was the one to lead Harry to the sword, and Snape has been the one protecting him all these years in Lily’s honor. As such, we know that Snape never quite fell out of love with Lily, and it emphatically shows when he adopts the same Patronus as hers.