Mobile Suit Gundam 00
You might be able to guess, but the Gundam franchise in general has much in common with Code Geass. Besides Gundam Seed, however, Gundam 00 is the series that has the most in common with Code Geass. The series takes place far in the future, where three superpowers have struggled for years over three massive solar energy stations that give the world its power. After decades of war a mysterious group named Celestial Being emerges with the sole goal of eradicating all war, through the use of war itself.
The members of Celestial Being make up the main cast of the show, and the four main characters each pilot a powerful Gundam mobile suit. As you might imagine, each of these characters have a past wrecked by the consequences of war, and an ambition to see its end. Gundam 00 is filled with politics, clashing ideologies, religious references, and massive battles. Like many Gundam series, and Code Geass, it’s about the war of ideals as much as it is mobile suits blasting each other apart. Rebellions and terrorism are just a couple of the central themes that Gundam 00 shares with Code Geass.