This short but revealing biography tells the story of Kurt Mendelssohn FRS, one of the founding figures in the field of cryogenics, from his beginnings in Berlin through his move to Oxford in the 1930s, and his groundbreaking work in low temperature and solid state physics. He set up the first helium liquefier in the United Kingdom, and did fundamental research that increased our understanding of superconductivity and superfluid helium.