What order should you watch Fullmetal Alchemist in?
There is no single required order, because the two television series are parallel tellings rather than seasons. Fullmetal Alchemist (2003) ran 51 episodes while the manga was still young, then finished with an anime original second half and a sequel film, The Conqueror of Shamballa (2005). Fullmetal Alchemist: Brotherhood (2009) ran 64 episodes and adapts the finished manga from start to end. Watching one does not spoil the other so much as reframe it.
For most new viewers the practical order is Brotherhood alone, followed by its film The Sacred Star of Milos (2011) as an optional side story set mid series. Brotherhood assumes some familiarity early on and retells the opening arcs quickly, then settles into the complete manga plot, including characters and a final battle the 2003 series never reaches because they did not yet exist in print.
The completionist order runs 2003 first, then its film, then Brotherhood. Seen in production order, you watch the franchise invent one ending under deadline pressure and then, six years later, deliver the ending Arakawa actually wrote. The 2003 series spends more time on early material, gives its supporting cast extra room, and its darker original villains only make sense inside its own continuity, ending with Shamballa rather than with episode 51.
Manga readers have a third path: read the 27 volumes, then treat both anime as interpretations. The 2003 series preserves early chapters most faithfully before diverging around the story's first third; Brotherhood compresses those same chapters, then follows the manga closely for its remaining fifty episodes. Four Brotherhood OVA shorts and a set of gag extras exist for both series and sit safely after everything else.
Avoid the one genuinely bad order: alternating episodes between series. Shared early scenes play out differently, character introductions assume different knowledge, and the two continuities contradict each other on core facts by their midpoints. Pick one telling, finish it and its film if it has one, then cross over.
