The coin, said to date from the dawn of English Christianity, was unearthed in East Grafton by a metal detectorist.
Richard Bishop, from auctioneers Spink and Sons, said the final sale price was a "magnificent achievement" for such a "small but perfectly formed gold thrymsa".
Wiltshire Museum bought the coin after a fundraising campaign.
It features a head motif with a Christian cross and is believed to have been struck in modern-day France.
Experts believe it was in circulation just after the burial of King Raedwald at Sutton Hoo around AD 625.
Only five examples of this type of coin have ever been found.
Wiltshire Museum director David Dawson, said they were "delighted" to have bought the "important coin", which he said will help experts understand the importance of the Vale of Pewsey and the Kingdom of Wessex in the Saxon period.
The museum had donations from all over the world, including grants from Arts Council England, Victoria and Albert Purchase Grant Fund and the Art Fund.
Stephen Deuchar, director of the Art Fund, said: "Very few coins of such quality exist...  It's a wonderful addition to the museum's collection."

The Daily Telegraph reported that the star would be dropped after an internal investigation concluded he had attacked a producer on the show.
It said director general Tony Hall would explain that such behaviour could not be tolerated at the BBC.
Clarkson tweeted a rebuttal of the story on Wednesday morning.
"Just to keep everyone up to date, I haven't heard a thing," he wrote, shortly before 10:00 GMT.
The BBC also says no final decision had been made on Clarkson's future.
"When we have an outcome, we will announce it," said a BBC spokesman.
Clarkson was suspended 16 days ago following an alleged "fracas" with producer Oisin Tymon.
The row was said to have occurred because no hot food was laid on for the presenter following a day's filming in North Yorkshire.
An internal investigation began last week, led by Ken MacQuarrie, the director of BBC Scotland.
Mr Tymon did not file a formal complaint and it is understood Clarkson reported himself to BBC bosses.
The BBC's director of television, Danny Cohen, felt he had no choice but to suspend the presenter pending an investigation.
The decision caused an outpouring of support from Top Gear fans, with more than a million people signing an online petition to reinstate him.
Whatever the outcome of the BBC's inquiry, the motoring show is expected to continue.
It is one of BBC Two's most popular programmes, and overseas sales generate an estimated £50m a year for the corporation's commercial arm, BBC Worldwide.
Whether Clarkson's co-presenters James May and Richard Hammond would continue in his absence has yet to be confirmed.
All three have their contracts up for renewal this year.
Meanwhile Radio 2 DJ Chris Evans, who has been touted as a potential replacement for Clarkson, has ruled himself out of the running.
"Not only is it not true, it's absolute nonsense," he told listeners on Wednesday morning.
"From what I've seen on Twitter and various social media, there's a 50/50 split approximately as to whether me being involved in the show is a good idea.
"In TV or radio, if you get a 50/50 love/hate reaction that usually equals massive hit. I used to work for [ratings body] Barb and knock on people's doors and this was the rule of thumb.
"However, I'm in the no camp. So regardless of whether it would be a hit, I'm voting a no for myself on that show, so that's never going happen.
"And that's the end of that."
Speaking later to reporters outside Radio 2, Evans refused to speculate on who else might replace Clarkson, saying he "doesn't know if the post is available yet".
An "excessively rare" Saxon gold coin that was discovered near a Wiltshire village has been sold for £21,600.
[NEXT_CONCEPT]
Top Gear presenter Jeremy Clarkson says he "hasn't heard a thing", after press reports suggested the BBC would sack him on Wednesday.