ITV is to buy the maker of Pawn Stars and Real Housewives Of New Jersey in a deal which boosts its production facilities in the largest TV market in the world.
The broadcaster, which is home to Downton Abbey and Coronation Street, is paying $360m for 80% of Leftfield Entertainment with an option to buy the remainder of the company.
Leftfield sold its first series in 2008 and now produces more than 300 hours of unscripted shows for over 30 US networks. Its acquisition means ITV is the largest independent unscripted producer of entertainment in the US.
Leftfield's Pawn Stars has topped the ratings on the History Channel for the last four years, and is its number one show worldwide.
Over the last 18 months ITV has snapped up a number of US production companies, including Gurney Productions, High Noon Entertainment and Thinkfactory Media, which have produced such programmes as Hatfields & McCoys, American Digger and Bakery Boss.
In the UK it has bought So Television, which is behind The Graham Norton Show, to build an arsenal of original content it can sell around the globe.
ITV has been looking to minimise its exposure to volatile advertising markets by boosting its spending on original content.
Its chief executive Adam Crozier said: "Leftfield is a fantastic success story, rapidly growing from a single pilot to become one of the biggest indies in the US."
ITV, which is four years into a turnaround plan, saw its profits rise 27% to £581m last year after revenues lifted 9% to £2.4 billion.
Much of the improvement came from its production arm, which grew revenues by 20% to £857m after the success of programmes such as Ant & Dec's Saturday Night Takeaway and The Chase.
Mr Selfridge, Poirot and Hell's Kitchen US were sold to more than 150 countries, while eight of its formats have been sold in three or more countries, including I'm A Celebrity Get Me Out Of Here! and Dancing On Ice.