Oh played the character of Cristina Yang on the ABC series, reported E!News.
"It's been a great privilege to play the character of Cristina Yang on GA and I am both sad and excited to see where this, her final season will take her," Oh said in a statement.
Series creator Shonda Rhimes said, "I can't quantify how grateful I am for her collaboration on a character we both love so deeply."
This is not for the first time that the series has witnessed a high-profile exit. Actors Katherine Heigl, Eric Dane and Isaiah Washington.