A buyer willing to pay around £6m for the sapphire and diamond coronet will have to be found in the next three months to stop the sale to a foreign buyer going ahead.
The temporary export ban was imposed by Culture Minister Matt Hancok to give time for an alternative buyer committed to keeping it in the UK to be found.
Designed by Prince Albert, the coronet matched the sapphire and diamond brooch that he gave her the day before their wedding.
She wore it at the state opening of Parliament in 1866, her first appearance at the occasion since the death of Prince Albert in 1861.
The coronet subsequently found its way to a dealer in London who sold it to the buyer now seeking to take it out of the country.
Mr Hancock said: “Queen Victoria’s coronet is stunning. It is one of the most iconic jewels from a pivotal period in our history and symbolises one of our nation’s most famous love stories.
“I hope that we are able to keep the coronet in the UK and on display for the public to enjoy for years to come.”
The temporary export ban expires on December 27 although it could be extended to June 2017 if there is a serious attempt to buy it.
The ban was imposed following a recommendation from the Reviewing Committee on the Export of Works of Art and Objects of Cultural Interest (RCEWA) because of its “outstanding significance”.
RCEWA member Philippa Glanville said: “Key to the self-image of the young Victoria, this exquisite coronet was designed by her husband Prince Albert.
“Worn in her popular state portrait by Winterhalter of 1842, the year it was made, its combination of personal meaning and formality explains why she chose to wear it in 1866, emerging from mourning for the State Opening of Parliament.
“It evokes vividly the shared romantic taste of the time, and its form has become familiar through many reproductions.
“Its departure would be a great loss, given its beauty, its associations and its history.”