The four-weekly flights will operate out of Gatwick from March 31, 2019, on board a Boeing 787-9 Dreamliner aircraft.
A Premium cabin will also be available on board the 344-seat aircraft with one way prices leading in at £550.
Outbound flights depart London at 12pm. arriving in Rio de Janeiro at 7.25pm while inbound flights depart Rio de Janeiro 10.25pm arriving 1:35pm at Gatwick.
Norwegian chief executive Bjorn Kjos said: “We’re building on our expansive global network by launching the UK’s most affordable flights to Brazil and making South America available to even more consumers.
“Our new Rio de Janeiro route breaks the monopoly on direct flights between the UK and Brazil as we’re committed to lowering fares and making travel more affordable for all holidaymakers and business travellers.
“Brazil is a fantastic addition to our global network and we look forward to welcoming customers on board.”
The new route to Rio de Janeiro follows Norwegian’s existing service to South America with direct flights from London to the Argentinian capital, Buenos Aires.
The Gatwick-Buenos Aires route will increase from four weekly flights to a daily service from December 3 in response to customer demand.