Jonassen is a surname. Notable people with the surname include:
Emil Jonassen (born 1993), Norwegian football player Fartein Døvle Jonassen (born 1971), Norwegian novelist and translator Hagbard Jonassen (1903–1977), Danish botanist, quaternary geologist, war resister and nuclear disarmament proponent Jess Jonassen (born 1992), Australian cricketer Kenneth Jonassen (born 1974), male badminton player from Denmark Vitus Jonassen Bering or Vitus Bering (1681–1741), Danish-born Russian navigator in the service of the Russian Navy
See also Jonassen Island, one of several Antarctic islands around the peninsula known as Graham Land Jonassen Rocks, small group of rocks lying off the south coast of South Georgia Joensen Johannessen Johnsen Jonasson Jonsson
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