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Wiltshire-based Rudman claimed victory in four minutes 38.60 seconds in the fourth and final run on Friday.
American Noelle Pikus-Pace took silver, finishing 0.57 seconds behind Rudman.
Canada's Sarah Reid secured bronze, finishing 0.13 seconds ahead of Britain's Lizzy Yarnold, who had to settle for fourth.
Rudman, 31, went into the final run with a 0.82 second lead over Pikus-Pace and held off her challenge in the final run to claim gold.
The 2006 Olympic silver medallist and  had earlier admitted she only considered this season to be a development year ahead of the 2014 Olympics in Sochi, Russia.
A fourth-place finish in 2011 was her previous best World Championships result.
Rudman wrote on Twitter: "Wow! I'm World Champion!"
In an interview with young daughter Ella in her arms, she added: "I hope I didn't scare you too much on that run.
"It went really well yesterday so I was more relaxed today but I still didn't expect to win until I finished."
Rudman is Great Britain's second world skeleton champion after Kristan Bromley, Rudman's partner, who won gold in Altenberg in 2008.
Shelley Rudman has become the first British woman to win skeleton gold in the world championships, in St Moritz in Switzerland.