The bestselling author regularly delights fans by adding magical facts, details and even slang to the fictional world.
But now she has revealed the biggest addition yet - four new schools to rival Hogwarts.
Avid readers will know that there are 11 major schools in the wizarding world, but until now the identities of only three were known - Hogwarts, located in Scotland, Durmstrang in northern Europe and Beauxbatons in France.
The new additions will be a welcome surprise to her followers across the world, as they indicate a much larger, more international magical community than previously thought.
She made the revelation on her site Pottermore, launched in 2013, which focuses on the unknown parts of the Harry Potter series.
The new institutions include schools in America, Brazil, Japan and Africa, and Rowling has hinted that the remaining four will be revealed in the future.
The first announcement was Mahoutokoro - an ancient Japanese centre located on the volcanic island of Iwo Jima.
According to Pottermore, wizarding children are flown back and forth to their homes every day on the backs of giant seabirds.
Students are presented with enchanted robes when they arrive, which change colour as the wearer learns magic.
The school also has an outstanding reputation for Quidditch, a popular game played on broomsticks, which students practice over turbulent seas in stormy conditions.
The next school, Uagadou, is an African institution at least a thousand years old and is the largest of all wizarding schools.
Rowling writes that the school is “carved into the mountainside and is shrouded in mist” - so much so that sometimes it “simply appears to float in mid-air”.
Instead of using wands, students here cast spells by “simply pointing a finger” or making a specific hand gesture.
Pupils only find out that they have been selected to attend the school when they are visited by a Dream Messenger, who will appear in their sleep.
Those lucky enough to be picked will wake up holding a token, usually an inscribed stone, which guarantees them a place.
The third school, Castelobruxo, is a Brazilian school located deep within the rainforest.
The golden building is protected by Caipora - small and furry spirit-beings who are extraordinarily mischievous and tricky.
Students at Castelobruxo wear bright green robes and are especially advanced in Herbology and Magizoology.
The final school to be revealed is Ilvermorny, located in North America. However, Rowling has not yet provided any extra detail about the institution.
In the online article, Rowling writes: “The precise location of each of the following schools is a closely guarded secret.
“As a general rule, magical schools tend to be situated in landlocked, mountainous areas, as such regions are difficult for Muggles [non-wizarding people] to access, and easier to defend from Dark Wizards.”