Last name 信吾 (信吾 
) , all over the world, is a very rare family name. The family name 信吾 is habitual in Eastern Asia, particularly China, where it is an extremely rare surname. More frequently, 信吾 is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| 信吾 | China |
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津田 信吾 Japanese businessman, JP (b. 1881) |
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鳥井 信吾 Japanese businessman, JP (b. 1953) |
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| 葛山 信吾 Japanese actor, JP (b. 1972) |
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