Residents chose the striking design of a Saltire overlayed with a black Nordic cross to represent them.
The design represents Sutherland’s unique position as the historic mainland frontier between Scotland and the Vikings.
The crossed form represents the sun at its highest point in the South and the origins of the county’s name as the Viking’s ‘South Land’.
The colours were inspired by those of the former Sutherland County Council.
Philip Tibbetts, honorary vexillologist to the Court of the Lord Lyon, said: “The meaning behind this flag, which I think is a real showcase of what good flag design is, has got a meaning that could only apply to Sutherland, not any other county in the country.
“This literally says this is a unique place in Scotland; the place being where Vikings and the ancient people of Scotland met and fought with each other.”
The design was selected after it attracted 29 per cent of more than 3,000 votes cast.
The flag formally was formally raised for the first time by a party of active and retired sailors from HMS Sutherland at a ceremony in Golspie.
Accompanied by the Sutherland Schools Pipe Band, the sailors were also joined by councillors, the Lord Lieutenant and the Court of the Lord Lyon.
The choice of flag went to a public vote after controversy surrounded the original selection made by the Sutherland Flag Commitee.
The Lord Lieutenancy launched a public vote after the committee’s original choice of a swooping eagle on a yellow background accompanied by three stars or mullets prompted some criticism.
The subsequent public vote was hosted by the Flag Institute to ensure best practice.
The official warrant to initiate the registration of the flag with Scotland’s heraldic authority, the Court of the Lord Lyon, has now been signed off.
The flag is now free for the public and businesses to fly.
Mr Tibbetts added: “It has been a fantastic response to the vote, with such a large number of the county voting and bringing things to a clear resolution.
“I have to thank the flag committee for reopening the competition for this vote, which has now been shown to have been the right decision.
“The winner is a great design and did well to win a very close vote. I also have to thank the county’s school pupils for putting in hundreds of entries, including two of the finalists, and being represented on the judging panel”.