In 1971, IBM introduced the first "memory disk", as it was called then, or the "floppy disk" as it is known today. The first floppy was an 8" plastic disk coated with magnetic iron oxide; data was written to and read from the disk's surface. The nickname "floppy" came from its flexibility.

Is was invented by Yoshiro Nakamatsu in 1950.
I guess it’s Alan Shugart.