The technical error has directed people searching for the national park more than 150m (241km) away to a location between Chelsea and Knightsbridge.
Brecon Beacons National Park Authority posted the image online with the caption: "We have now moved. Londoners get an upgrade thanks to Google Maps."
Chief executive John Cook joked: "Well the move has come as a bit of a shock to us all."
He added: "I'm sure it will come as good news to Londoners who want some fresh mountain air on their doorstep.
"The truth is we are only three hours away from London - don't rely on your sat-nav or Google Maps - just head to Bristol on the M4, cross the bridge, ask a local and they'll know exactly where to find us."

The six-year strategy aims to produce 15 new cars or derivatives of existing models and lift annual sales to as much as 5,000 cars, from 1,600.
At least half of the cars will have hybrid engine technology.
McLaren Automotive, which draws on technology used by the F1 racing team, was launched just six years ago.
Mike Flewitt, McLaren Automotive's chief executive, told the BBC: "This business plan confirms that McLaren Automotive will remain proudly and fiercely independent by continuing to build the world's finest two-seater sports and supercars."
But he added that plan, called Track 22, was also about broadening the Uk supercar maker's customer base with a new range of cars more attractive to the rich - rather than just the super-rich.
The company is responsible for supercars including the £1m petrol-electric hybrid McLaren P1, but has already started introducing cheaper models.
This includes the launch at the Geneva Motor Show of the £150,000-plus 570GT, which is pitched at some rival cars produced by Ferrari and Porsche.
Rather than being a racing machine, Mr Flewitt says the 570GT is designed to give a more relaxed drive, and has been designed with a more comfortable suspension. It also has more luggage capacity.
"We see this [car] as being very easy to drive on a day-to-day basis," Mr Flewitt said.
About a quarter of the new £1bn investment will go directly into research and development, Mr Flewitt said. This will include work on an all-electric prototype. Electric sportscar technology is advancing fast, led by the likes of Tesla.
He also hopes that the new range of cars will bring down the age profile of a typical McLaren buyer, which is 40-plus in Europe. However, the typical Chinese buyer is in his or her 20s.
The Track 22 plan will involve McLaren Automotive adding about 500 staff to its existing 1,500. A second production shift has already started at the company's factory at Woking, Surrey, and a recruitment drive has begun.
Many of the jobs will be skilled engineering roles. Mr Flewitt said the market for good engineers is "undoubtedly getting more competitive." But he added: "Luckily, McLaren is an attractive brand to come and work for."
More than 90% of McLaren's output is for export, and the company has seen sales fall in China as the economy slows.
Is he worried about the health of the global economy? "You worry about it all the time. The strategy we took was to make sure we had broad distribution.
"We sell cars into 30 markets, with 82 dealerships. As one market comes down - China has dropped this year and last year - other markets strengthen," he said.
A glitch on Google Maps has located the Brecon Beacons in the heart of London.
[NEXT_CONCEPT]
McLaren Automotive, part of the F1 group, has unveiled a £1bn expansion plan to produce up to 15 new models and recruit 500 staff.