Shoppers are expected to spend an incredible £649.6 million this Cyber Monday, according to figures from the Centre for Retail Research.
The online equivalent of Black Friday, which took place on November 28 - Cyber Monday is a great time to snap up a bargain.
But where can you find the best deals? Let's find out...
What is Cyber Monday?
Cyber Monday started in the US and is the first Monday after the country's Thanksgiving celebrations.
Crucially, however, it is also the first Monday after most people's last pre-Christmas payday.
And that makes it a huge day for online retailers in the UK too, which is why many of them offer discounts to entice shoppers away from the competition. This year, Cyber Monday falls on Monday, December 1.
Where can I find the best deals?
There will be lots of special online offers available on Monday. Here is a selection of some of the best.
Internet giant Amazon is planning to release hundreds of limited "Lightning Deals", which offer discounts for a specific period, with new offers coming online every 10 minutes.
Details of Amazon's Lightning Deals are only released as the offers become available.
However, recent Lightning Deals have included up to 50% off Scalextric sets and up to 60% off diamond jewellery, and deals on the day are expected to include discounts on TomTom Sat Navs, ruby jewellery and the Harry Potter Hogwarts Collection DVD.
Amazon said: "Cyber Monday is fast approaching and we are excited to bring you deals in electronics, video games, clothing, toys, and more."
Feeling charitable? If you are, Cyber Monday is a great time to shop on the Apple website, as the company is running a promotion that involves it donating money to the fight against AIDS for every purchase made.
The offer is being run to mark World AIDS Day, also on December 1.
Apple said: "We'll contribute a portion of the proceeds from every product, accessory and gift card we sell to the Global Fund to fight AIDS."
The online fashion store is offering 20% off everything until 8am on Tuesday, December 2.
All you have to do is enter the code CYBERWKND20 to claim the discount on your Cyber Monday purchases.
The site is promising a range of Cyber Monday deals along the same lines as its Black Friday weekend offers, which include Playstation 4 and Xbox One packages for £299.99.
The best of the rest
Many of the Black Friday deals offered by retailers last until Cyber Monday - and even beyond.
John Lewis, for example, is offering £150 cash back on Bosch appliances bought before December 12, plus an extra £50 back if you buy a a washing machine and a tumble dryer.
Elsewhere, Microsoft's digital content sale lasts until Monday, with Xbox Live Gold members able to get a whopping 75% off games.
And mobile operator O2 is offering Black Friday/Cyber Monday deals that last all week, including the chance to get £99 off a Samsung Galaxy S5 by signing up to its £33-a-month tariff.
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