The 416-bedroom Lancaster London (pictured) and 220-bedroom K West hotel & spa will be cutting their prices by 50% for one day only on Black Friday.
The sister hotels, owned by Thai company the Landmark Group, will be participating in the discount event, which has taken the UK retail sector by storm in recent years.
Black Friday has become the biggest shopping day of the year and on Friday 27 November both four-AA-star hotels will be trying to get in on the action.
The Black Friday flash sale will start at 9am and will be available online only for 24 hours, with discounts applicable for stays from 20 December 2015 to 31 March 2016.
British consumers spent £810m on online purchases alone on Black Friday last year. This year internet sales over the 24-hour period are expected to be more than £1b for the first time in UK history.