Family name Washiyama (Washiyama 
) , worldwide, is a very rare cognomen. The surname Washiyama is habitual in Singapore, where it is a rare surname, Canada, where it is an extremely rare surname, and Peru. Measured by absolute frequency, it is commonest in Singapore, the United States, and Canada.
| VARIANT | COUNTRY |
|---|---|
| Washiyama | Canada, Brazil, Peru, Singapore, United States |
| kyōhei washiyama (b. 1872) |
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| kohshin washiyama researcher (ORCID 0000-0002-9908-8756) |
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| kouhei washiyama physicist |
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| kazuki washiyama (b. 1995) |
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