How long did it take Andy Warhol to paint Marilyn Monroe?

Andy Warhol painted several versions of Marilyn Monroe, but his most famous series, "Marilyn Diptych", took him about 4 months to complete. He started working on it in June 1962 and finished in October 1962.

However, it's important to note that Warhol created many other Marilyn Monroe paintings and silkscreens throughout his career, some of which were completed much quicker.