Bargain hunters began lining up outside shops in Argyle Street, Buchanan Street and Sauchiehall Street – as well as malls – in the early hours.
Shoppers began queuing up outside Next, at the corner of Queen Street and Argyle Street, before 5am.
Next opened at 6am, offering customers at least 50% off all its sale items, while Marks and Spencer opened at 8am to offer shoppers cut-price goods.
Shop windows across the city's Style Mile were awash with sale signs as consumers began swiping up reductions of up to 80% in some stores.
Despite some shops, including Currys/PC World, kicking off their sales two days earlier than normal on Christmas Eve, the traditional Boxing Day sales are still billed as the main event.
Retail bosses were hoping to see record numbers of shoppers flooding through their doors.
In total 14million people – one in four – in the UK are expected to head into stores and the high streets, hoping to spend their cash on heavily-discounted stock. Shoppers are predicted to spend £2.9billion in today's sales.
The city's malls at Silverburn and Glasgow Fort, Easterhouse, were also expecting a huge surge of shoppers. Bosses at Silverburn predict about 55,000 people will come through the doors.
Last year almost a thousand early birds lined up outside the centre for the opening of Next Silverburn at 6am – and almost the same amount of shoppers queued today.
The crowds of shoppers will spend most of their money on clothes, but electrical goods, handbags, bedding and shoes will also be high on shopping lists.
Braehead Shopping Centre was also buzzing as Next, JD Sports and Starbucks began trading at 6am.
They were followed by Topshop, Topman and Marks and Spencer at 8am, along with McDonald's at 8.30am and River Island at 9am.
Peter Beagley, general manager of Braehead, said: "A busy Braehead on Boxing Day is as traditional as the turkey sandwiches lots of people will be having from the leftovers from Christmas dinner.
"Although normal trading does not start until 10am, we always open the centre before the sun rises."
Meanwhile, House of Fraser opened its doors at 8am, and cut prices by up to 70%.
Department store Debenhams kicked off the clearance with a special two-day launch event with all women's, men's and kids' coats, jacket, knitwear and boots available in its sale for half price or less. Its store in Argyle Street, Glasgow, opened at 7am.
John Lewis kicked off its online sale at 5pm on Christmas Eve, but its shops remained closed today.
GUIDE TO THE SALES – PAGES 21-28