The Rains of Castamere (Season 3, Episode 9)

"The Rains of Castamere", sometimes referred to as "The Red Wedding," is the ninth and penultimate episode of the third season of HBO's fantasy television series Game of Thrones, and the 29th episode of the series. The episode was written by executive producers David Benioff and D. B. Weiss, and directed by David Nutter. It aired on June 2, 2013.

The episode is centered on the wedding of Edmure Tully and Roslin Frey, one of the most memorable events of the book series, commonly called "The Red Wedding", during which Robb Stark and his banner-men are massacred. Other storylines include Bran Stark's group having to separate, Jon Snow's loyalties being tested, and Daenerysplotting her invasion of the city of Yunkai.

https://en.wikipedia.org/wiki/The_Rains_of_Castamere