The Mid Berwickshire councillor, of the Conservatives, was announced at a full council meeting today (November 25).
Mr Rowley will take over from Shona Haslam who announced on November 12 that she would be stepping down after four years at the helm.
He was nominated for the role by Kelso representative Simon Mountford, also of the Conservatives, seconded by independent Galashiels councillor Sandy Aitchison.
Mr Mountford told the meeting that he was confident Mr Rowley will lead the council with “panache and wisdom”.
Addressing the chamber, Mr Rowley said: “I think election day in 2017 was the most humbling day of my life being elected by my neighbours and constituents, and this probably trumps it.
“I’d remind myself and everyone else that the position is leader of the council. It’s not leader of the Conservative group, it’s not leader of the administration.
“We’re in incredibly difficult times. Our staff are incredibly stretched, every officer in the council is working incredibly hard, we’re under-resourced in terms of funds from government.
“We do have great opportunities but those opportunities require a great deal of work.”
Describing himself as “probably the first openly gay leader” of SBC, Mr Rowley expressed a desire to continue promoting diversity.
Mr Rowley – who is the council’s executive member for economic regeneration and finance, as well as the chairman of the South of Scotland regional economic partnership – said that there would be a reallocation of responsibilities at the council’s next full meeting in December to “spread the load”.
Tweeddale East councillor Stuart Bell, leader of the opposition, said that the SNP group “will be working collaboratively through the remaining months of this administration”.
There is a local government election in May next year.
Mrs Haslam will remain an elected member for Tweeddale East until that time.
Council convener David Parker thanked Mrs Haslam for the work she has carried out since 2017.
“It has been an incredible period for the council with the pandemic and a range of challenges but Shona rose to those significantly,” he said.