Boris Caesar Wilhelm Hagelin (2 July 1892 – 7 September 1983) was a Swedish businessman and inventor of encryption machines.

Born of Swedish parents in Adshikent, Russian Empire (now Azerbaijan), Hagelin attended Lundsberg boarding school and later studied mechanical engineering at the Royal Institute of Technology in Stockholm, graduating in 1914.

That design was small, cheap and moderately secure, and he convinced the US military to adopt it.

After his company, Crypto AG, was secretly sold to foreign intelligence agencies (the American CIA and German BND) in 1970, it fraudulently sold compromised machines to a variety of customers, including governments.

[4] Boris is the great-grandfather of Carl Hagelin, former NHL player for the Washington Capitals.