Joan Elizabeth Curran (26 February 1916 – 10 February 1999) was a Welsh physicist who played important roles in the development of radar and the atomic bomb during the Second World War. She invented chaff, a radar countermeasure technique credited with reducing losses among Allied bomber crews. She also worked on the development of the proximity fuse and the electromagnetic isotope separation process for the atomic bomb. In later life she became a founding member of the Scottish Society for the Parents of Mentally Handicapped Children.