Nissen may refer to:

• a creature in Norse mythology, see Tomte.
• a building shaped like a tube cut in half along the middle and made from corrugated iron sheets, see Nissen hut.

People named Nissen include:

• George Nissen (born 1914) inventor of the modern Trampoline
• Georg Nikolaus von Nissen (1761–1826), Danish diplomat and writer, known as a biographer of Wolfgang Amadeus Mozart
• Hans Joerg Nissen (born 1935), German archaeologist.
• Peter Norman Nissen (1871–1930), Canadian mining engineer.
• Rudolf Nissen (1896–1981), German surgeon and inventor of the Nissen fundoplication.
• Sönke Nissen (1870–1923), German industrialist and philanthropist.
• Steven E. Nissen (born 1949), heart specialist and chairman of cardiovascular medicine at the Cleveland Clinic.