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Billy Katagiri
Name: Billy Katagiri
Japanese: ビリー・カタギリ
Genetic Type: Human
Gender: Male
Birthday: April 24
Age: 31 (Season 1)
36 (Season 2)
38 (Movie)
Blood Type: AB
Height: 189 cm
Weight: 69 kg (Season 1)
70 kg
Nationality: Union of Solar Energy and Free Nations
Love Interest: Leesa Kujo
Family: Homer Katagiri (uncle, deceased (S2))
Mehna Carmine (wife, cca. Movie)
child (unnamed, cca. Movie Novel)
Affiliation: Earth Sphere Federation Army
Prev. Affiliation: Celestial Being (cca. S2)
A-Laws (S2)
Innovators (S2)
Overflags (S1)
Occupation: Engineer
Prev. Occupation: SIGNS OF ZODIACS : TAURUS ♉
Designation: Chief Technologist
Voiced by: Yūji Ueda (Japanese)
Kirby Morrow (English)

Billy Katagiri (ビリー・カタギリ, Birī Katagiri) is a fictional character in the anime, Mobile Suit Gundam 00. Billy was an engineer working for the Mobile Suit Warehouse and Development (MSWΛD), who got transferred into the Overflags during the start of Celestial Being's armed intevention. Five years later, he joined the A-Laws to fight against Celestial Being. He later helped the Innovators develop their mobile suit prior the Battle of Lagrange 2. After the defeat of the A-Laws and Innovators, Billy joined the Earth Sphere Federation as one of their chief military technologist.