The ice cool speed queen smashed the women's course record on Thursday to hold the midway lead and went even faster in heat three to widen the gap to the chasing pack led by Canadian favourite Mellisa Hollingsworth.
With a 0.52 second cushion going into her final slide Williams kept it clean through the 16 curves to win Britain's first Winter Games gold from an individual sport since Robin Cousins won the figure skating title at Lake Placid in 1980.
Hollingsworth's gold medal dream ended in despair when she crunched into a wall in the middle of her final run meaning Germany's Kerstin Szymkowiak took the silver and compatriot Anja Huber the bronze.
But Williams then had an anxious wait after Canada appealed against the legality of her crash helmet.
The appeal was rejected by the International Bobsleigh Federation.
The United States had a similar complaint against Williams's helmet thrown out by race officials after the first two runs. They argued that her helmet had illegal aerodynamic features which are banned by the FITB.
In rejecting the appeal, the FITB said: "After an inspection of the helmet by the jury, it was determined that according to the helmet manufacturer, spoilers were an integral part of the helmet.
"FITB rules state that a safety helmet should not have any additionally attached aerodynamic elements or adhesive tape (except that used to fix the visor and the goggle strap) and has to be without any spoilers or edges that stick out."
Williams is the first female Brit to top the podium since Jeannette Altwegg won skating gold at Oslo 1952 and she did so at a canter.
With a lead of 0.30 at the midway stage Williams cannot have slept easy, but if she tossed and turned she did anything but back on the track, clocking 53.68 and 54.00 in her two runs for a combined time of 3:35.64 minutes.
"It was all a bit of a blur in the final run, I can't remember half of it but I looked up at Andi Schmid [British Skeleton performance director] and he was smiling so I thought it must have been good," she said.
"I was bit nervous because I was the last one left in the changing room but I thought I had nothing to lose so I tried to enjoy it and, you know what, it was great."
Williams has a penchant for fast tracks and they don't come quicker than the one in Whistler - bathed in controversy after the tragic death of Georgian luger Nodar Kumaritashvili in a training accident.
The newly-crowned champion is not a household name in the UK just yet, and while that is all about to change, few should be surprised by her success.
Williams is the current world silver medallist having finished second in Lake Placid - a track not too dissimilar to Whistler's and she was second in the three of the last four training runs.
Meanwhile, time ran out for Olympic silver medallist Shelley Rudman, who, seventh overnight, clawed her way back into medal contention consistently improving her times, only to end up sixth.
Four years ago Williams was a watching reserve as Rudman sprung silver in Turin - she was a spare part and consoled herself with a spot of work for the British press.
Now she will be writing the headlines. In taking gold she has stepped out of Rudman's shadow and continued Great Britain's rich Olympic skeleton form.
Great Britain have now managed a medal at the five Winter Olympics in which skeleton has been on the programme but Williams is the first to take gold.