Russia's Tatyana Chernova won gold ahead of Ennis-Hill at the 2011 championships in Daegu, but has had her results annulled for doping.
Chernova was banned in 2015 for two years, stripped of two years of results, up to August 14, 2011, and must now forfeit the world title that she won two weeks later.
In response to the news, Ennis-Hill posted a photograph on her Instagram account of Chernova celebrating after the final event of the 2011 heptathlon, the 800m.
She wrote: "This image was forever imprinted in my mind. However, much it drove me on for what I was about to achieve at my first Olympics in London, in my heart I just knew it was wrong.
"So happy to finally be receiving my gold medal. Triple world champion, wow!"
The 30-year-old announced her retirement from athletics in October.