Season nine of Smallville, an American television series, began airing on September 25, 2009.This is the fourth season to air on the CW television network. Following the end of season eight, Aaron Ashmore and Sam Witwer departed the series after they were both killed off in the season’s finale "Doomsday". Season nine regular cast members include Tom Welling, Allison Mack, Erica Durance, Cassidy Freeman, and Justin Hartley, along with newcomer Callum Blue.

This season Clark takes his superhero persona into obsessive territory when he leaves behind those he cares for so that he can focus solely on Jor-El's training. In order to accomplish this, Clark wears a new costume that sports his family crest on the chest. The theme of the season is about Clark finally embracing his alien heritage, while also being his darkest hour thus far. As a result, Clark's relationship with Chloe and Oliver will suffer this season. Season nine will also see the introduction of more DC Comics characters, including multiple episode appearances for the Justice Society of America, villain Metallo, and villainess Agent Amanda Waller.

After four seasons broadcasting on Thursday nights at 8:00 pm, Smallville was moved to Friday nights at 8:00 pm for season nine,with the season premiere averaging 2.58 million viewers and outperforming any other show in the Friday 8:00 pm timeslot in over a year.[6] Furthermore, "Absolute Justice", a two-hour episode featuring the Justice Society of America, aired on February 5, 2010,receiving 2.77 million viewers.[8] It is Smallville's highest-rated episode for season nine in total viewers, adults 18-49 and men 18-49 so far.