Cummings was originally missed off the list of riders representing GB on the road, but has now received a call-up after Peter Kennaugh withdrew himself from the event.
“I've shown over the 2016 season to date that I am in great shape and I look forward to going to Rio to represent my country and hopefully we as a team come back with a medal from the road race," said Cummings.
The 35-year-old from the Wirral has taken four major victories this season alone, including stage seven of the Tour de France. The hilly Rio road race circuit looks on paper to suit his attacking style.
The omission of Cummings's name from the original list of GB competitors did raise eyebrows, and Cummings himself questioned GB's selection procedure.
Kennaugh voluntarily dropped out of the team after struggling to regain full race fitness in the wake of breaking his collarbone during the Tour of California in May.
"London 2012 was one of the highlights of my career so I am gutted to be missing out on Rio but, knowing that I am not able to give my best, I felt it was my duty to withdraw."
Cummings will join Chris Froome, Geraint Thomas, Adam Yates and Ian Stannard in GB's five-man line-up for the road race. Froome is also likely to ride the individual time trial.
Watch: Steve Cummings win Tour de France stage seven
GB men's road race coach Rod Ellingworth commented: “As always when selecting a team for a road race, the ideal situation is to leave the decision as late as possible as it’s difficult to predict riders’ form and health so far out.
“Since the selection panel made the original decision, there’s been 38 days of WorldTour racing during which time we’ve had some excellent results from the British Cycling squad, for example we’ve had British riders wear the yellow, green and white jerseys at the Tour de France.
“I’m confident that with this team, Team GB can be competitive at the men’s road race in Rio.”
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