The Bank of Scotland was founded by an Act of the Scottish Parliament on July 17 1695, a year after the Bank of England was established.
The 320th birthday comes in a milestone year for owners Lloyds Banking Group, with 2015 also marking the 200th anniversary of subsidiary Scottish Widows and the 250th anniversary of Lloyds Bank.
Mike Moran, director at Bank of Scotland, said: “A lot has changed since 1695, but building relationships with our customers and helping them make the right decisions, both big and small, is just as important to us today as it was right at the very beginning.
“Our focus on serving the needs of the people, communities and businesses of Scotland is stronger than ever. We are Scotland’s relationship bank, part of the fabric of everyday life, and we’re very proud of how far we’ve come.”