The possible deal was reported by the technology blog All Things D and by The New York Times, citing unnamed sources with knowledge of the matter.
The size of the deal would put it well above Google Inc.'s largest acquisition to date, its 2008 purchase of DoubleClick for $3.2 billon.
Groupon, a 2-year-old startup based in Chicago, offers daily local bargains ranging from yoga classes to discounts from national retailers.
Google and Groupon had no comment Tuesday.
