Upshot–Knothole Harry (UK#9) was a nuclear weapons test conducted by the United States as part of Operation Upshot–Knothole.

It took place at the recorded time of 04:05 (05:05 hrs [1]) hours, on May 19, 1953, in Yucca Flat, in the Nevada Test Site.

The sponsor of the test was the National Laboratory of the United States of America located at Los Alamos.

[7] The concept was termed as "radical implosion system" aiming towards reducing the amount of fissionable materials present in the weapon's core while generating moderately high yield.

By the end of 1980, as ascertained by People magazine, 91 of them had developed some form of cancer and 46 had died of the disease, including the main stars John Wayne and Susan Hayward.