What was the first video game in the Batman "Arkham" series?

The first video game in the Batman: Arkham series is Arkham Asylum because it introduced players to the dark and immersive world of Gotham City's infamous psychiatric hospital. Developed by Rocksteady Studios and released in 2009, Arkham Asylum revolutionized superhero games and set the foundation for the critically acclaimed franchise by combining a gripping storyline, strategic combat, and innovative gameplay mechanics. It allowed players to step into the shoes of the iconic Batman as he confronted some of his most notorious adversaries within the confines of Arkham Asylum, making it a groundbreaking and memorable entry in the series.