Gundam SEED Astray is a collection of gaiden (side-stories) set in the Cosmic Era of Gundam SEED.

Whereas the main story of Gundam SEED focuses on the struggles between the Earth Alliance, ZAFT, and Orb , the Astray series is focused on the three MBF-P0x mobile suit prototypes and their respective pilots and organizations, who mainly exist on the outskirts of the main SEED storyline. The MBF-P03 Gundam Astray Blue Frame is piloted by Gai Murakumo of the mercenary unit Serpent Tail. The MBF-P02 Gundam Astray Red Frame is piloted by Lowe Gear of the Junk Guild. (The third Astray, MBF-P01 Gundam Astray Gold Frame is shown in manga as well, but does not have it's own manga focused on it.) Astray R follows the adventures of the Red Frame's pilot Lowe and his Junk Guild associates. It is in manga format, and is set to be released in the US early 2005. Astray B follows Gai Murakumo and his fellow Serpent Tail mercenaries. It was released in Dengeki Hobby modelling magazine as a "photo novel", and it is highly unlikely it will make it over to the US.

In addition to Astray R and Astray B, there are three other Astray manga series. Gundam SEED Astray follows both stories, but primarily focuses on Lowe and the Junk Guild. Gundam SEED X Astray is about Canard Pars, who is a failed experiment from the Ultimate Coordinator program. Canard is searching for Kira Yamato, the successful Ultimate Coordinator, so that he can defeat him and prove he was not a "failure". During his search, he fights anyone he comes across. This brings him into conflict with Lowe Guele and the Junk Guild, who find a small boy named Prayer Reverie. Prayer has with him a powerful ZAFT prototype mobile suit, the YMF-X000A Dreadnought, which was built on a heavly modified GuAIZ frame and was the testbed for the DRAGOON (Disconnected Rapid Armament Group Overlook Operation Network) System of the ZGMF-X13A Providence. The latest Astray manga is Gundam SEED Destiny Astray, which is currently serializing in Gundam ACE. Destiny Astray focuses on Jess Rubble and his Gundam Astray Out Frame. The Astray Out Frame was found by Lowe and given to war photo-journalist Jess Rubble.