Vasilisa (Василиса) is the Russian feminine of Vasilios — from the Greek basilissa, meaning "queen." Vasilisa the Beautiful (Vasilisa Prekrasnaya) is the heroine of the most famous Russian fairy tale, who survives Baba Yaga's tests with the help of her magical doll.
Vasilisa is widely used in Russia.
Vasilisa does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
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In Pythagorean numerology the letters of Vasilisa reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.