Last name Klaas (Klaas 
, Клас 
, Клаас ) , globally, is a common family name. The surname Klaas is habitual in Estonia, where it is quite a common surname, South Africa, and Germany, where it is quite a rare surname. In absolute terms, the name is most common in South Africa, Germany, and the United States. Likewise, Klaas is the forename as well as the last name.
| VARIANT | COUNTRY |
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| Klaas | United States, South Africa, Belgium, Germany, Netherlands |
| Клас | Ukraine, Russia, Kyrgyzstan, Kazakhstan |
| Клаас | Ukraine, Russia, Kazakhstan |
Claas, Claus, Glas, Klaes, Klaus, Klausová, Klaâ, Klås, Nicholas, Niclaas, Niclaes, Nicolaas, Niklaas, Nikolass, Κλάους, Νίκολας, Νικόλαος, Νικόλας, Клаус, Мікалай, Никола, Николаев, Николас, Ніколас, ניקולס, קלאוס, كلاس, كلاوز, كلاوس, كلوز, كلوس, نيكولاس, کلاس, คลาศ, ნიკოლასი, クラウス, ニコラス, 克拉斯, 尼古拉斯, and 尼古拉耶夫
| adolf klaas DE (b. 1836) |
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| aleksander klaas Estonian clergyman, EE (b. 1868) |
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| julius klaas 28 February 1888 — 20 October 1965 (b. 1888) |
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| walter klaas German judge, DE (b. 1895) |
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| walter klaas German theologian, DE (b. 1904) |
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birute klaas-lang Estonian linguist, EE (b. 1957) |
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| werner klaas Association footballer (1914-1945), DE (b. 1914) |
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urmas klaas Estonian politician, EE (b. 1971) |
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| jean klaas French physician and activist for the Flemish cause, FR (b. 1925) |
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| hans klaas German entrepreneur, DE (b. 1927) |
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kristi klaas Estonian environmental official, EE (b. 1980) |
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| anne marie elisabeth klaas (born 1933) (b. 1933) |
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kathrin klaas German hammer thrower, DE (b. 1984) |
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max klaas German percussionist, DE (b. 1993) |
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| dieter klaas DE (b. 1959) |
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