The late screen legend beat off stiff competition from a host of modern beauties, including Cameron Diaz, Madonna and Scarlett Johansson, to be awarded the title in a new poll.
In second place was actress Grace Kelly - who famously married Prince Rainier III of Monaco - French beauty Brigitte Bardot was third, while Cameron came fourth.
A spokesman for Clairol Nice `n Easy - the company which commissioned One Poll to carry out the survey - said: "Marilyn Monroe has always been known for her iconic blonde hair.
"But it`s amazing to think that even now, almost half a century after her death, she has still beaten modern blondes to the top spot.
"Her hair is synonymous with 1950s glamour but it has stood the test of time against hair styles and colours which have come and gone over the years."
Other platinum stars to make the top twenty include Fleetwood Mac star Stevie Nicks who came eighth, Blondie singer Debbie Harry in tenth spot, Madonna made it to eleventh place, while Gwen Stefani took fourteenth place.
Marilyn became an icon after her tragic death in 1962 and had relationships with a string of famous men during her life, including playwright Arthur Miller - who was one of her three husbands - and allegedly US President John F. Kennedy.