Rat spleen is a common ingredient used in the preparation of various potions. It a required ingredient in the Shrinking Solution and in Dragon dung Fertiliser.

In 1993, Neville Longbottom added too many rat spleens and too much leech juice into his Shrinking Solution, making it posionous. Hermione Granger helped Neville fix the potion before Professor Snape had a chance to test it on Neville's toad, Trevor.

Appearances

• Harry Potter and the Prisoner of Azkaban (First appearance)
• Harry Potter and the Prisoner of Azkaban (video game) (GBA version only)
• Harry Potter and the Half-Blood Prince (video game)
• The Road to Hogwarts Sweepstakes