The sum is a world record for a work by Carriera, who died in 1757 aged 84, according to Cheffins auctioneers in Cambridge.
The painting, a portrait of British politician Coulson Fellowes, who was MP for Huntingdonshire from 1741 to 1761, had a pre-sale estimate of £15,000 to £25,000.
It was the first time the artwork had come to market since it was painted 301 years ago and it was sold to a private UK-based collector on the telephone.
It had remained in the family of Fellowes until the auction.
The portrait was made in 1724 and recorded in Carriera’s diary when Fellowes visited her Venetian studio on the Grand Tour during the years of 1723 and 1725.
Fellowes is shown in the portrait as a young man of 28, before he later became an MP.
Carriera was one of the most fashionable artists of her day and known to have created portraits of many notable figures, including Louis XV of France, English author Horace Walpole and French painter Antoine Watteau.
The previous record for a painting by Carriera was £421,250 for a portrait of Irish soldier and politician Gustavus Hamilton which was sold in New York in 2002, Cheffins said.
Luke Bodalbhai, paintings specialist at Cheffins, said: “This was a particularly elegant study by Rosalba and really exhibited her talent as one of the leading lights of 18th century portraiture.
“The piece was fascinating in that it had been created by one of the most interesting artists of the period, but also during some of the most pivotal years for British and European art and travel.
“As one of the first women to achieve international fame in portraiture, Carriera remains a trailblazer in art history, and it was a privilege to be able to offer this important work to the market for the first time.”
Fellowes was the son of barrister William Fellowes of Eggesford, Devon and, on his father’s death in 1725, inherited Eggesford Manor.
The portrait was part of the Fellowes’ family collection at Shotesham Park in Norfolk until the sale of the house and estate following the death of Major Charles Fellowes in 1979 but remained in the family, being offered for sale now for the first time since its execution.
Works by Carriera are currently held in The Louvre in Paris, The National Gallery in London, The Frick Collection in New York and other major galleries and institutions worldwide.
The £508,000 that the painting fetched when it was sold at auction on Wednesday includes the buyers’ premium and VAT.
