Hannes Olof Gösta Alfvén (30 May 1908 – 2 April 1995) was a Swedish engineer and physicist who won the 1970 Nobel Prize in Physics for his groundbreaking research on magnetohydrodynamics (MHD). His discoveries led to advancements in plasma physics and our understanding of phenomena such as aurorae, magnetic storms, radiation belts, the magnetosphere and cosmic plasmas.