Purple Wedding
From A Wiki of Ice and Fire

The Purple Wedding is the fan-given nickname for the wedding between Joffrey Baratheon and Margaery Tyrell that took place on the first day of the new century, 300AL AC. The wedding was a lavish affair, but ended in disarray when the King Joffrey drank a chalice of wine that poisoned with the Strangler and died quickly. Unlike the Red Wedding, this wedding is not called so in the books.