Ms Sturgeon received the Royal Warrant - formal approval of her appointment - at the Court of Session in Edinburgh.
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The formal proceeding, which took place before 15 senior judges, came less than 24 hours after MSPs at Holyrood elected the former deputy first minister as the new head of the Scottish Government.
She is due to take First Minister’s Questions at the Scottish Parliament for the first time in her new role this afternoon.
Ms Sturgeon succeeds Alex Salmond, who announced he would step down after a majority of voters rejected independence in September’s referendum.
The appointment sees the Glasgow Southside MSP make history by becoming Scotland’s first female leader.
Ms Sturgeon declared it had been “a very special occasion” as she left the court shortly after the ceremony.
Her formal appointment as First Minister and Keeper of the Scottish Seal took around six minutes in Court One of the Parliament House building.
It took place before a “full bench” of 15 judges and was presided over by the Lord President of the Court of Session and head of the Scottish judiciary, Lord Gill.
Proceedings were watched by various figures from the worlds of politics and law, including Ms Sturgeon’s husband Peter Murrell and Lord Advocate Frank Mulholland QC.
During the ceremony, the Lord President called for the royal warrant to be read to the court by the principal clerk.
Ms Sturgeon then bowed her head in agreement as she was asked to “solemnly, sincerely and truly declare and affirm that you will well and truly serve Her Majesty, Queen Elizabeth, in the office of First Minister of the Scottish Government”.
Following the official proceedings, Lord Gill told her: “On behalf of the court, I have the honour to congratulate you on your appointment as First Minister of the Scottish Government.
“You are now holder of one of the great offices of state.
“That is a great honour that will bring many arduous responsibilities but I hope that, notwithstanding the burden, the office of First Minister will give you great pleasure and fulfilment and I wish you well.”
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