|Season||Magical Girl Lyrical Nanoha StrikerS|
|Airdate||August 19, 2007|
"Decisive Battle" (「決戦」 Kessen) is episode 21 of Magical Girl Lyrical Nanoha StrikerS. It was originally broadcast on August 19, 2007.
From Yuuno's research, the Saint's Cradle is expected to be unstoppable if it reaches orbit and absorbs the power of two moons. Nanoha and Vita invade the Cradle, Hayate attempts to deal with the units outside, and Fate attacks Scaglietti's hideout. Signum and Rein go to battle Knight Zest and Agito, while the Forwards fight the cyborgs and Lutecia on the ground.