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  The world champions, who won Britain's first gold of the London Games in 2012, led from the start as they finished 1.2 seconds clear of New Zealand in a time of seven minutes 18.29 seconds.
  Denmark finished third to take bronze.
  It was Great Britain's 17th medal of the Games and moved them up to fourth in the table, ahead of Australia.
  Watch: TV wildlife presenter Steve Backshall breaks down in tears as fiance Helen Glover takes gold
  Britain's 18th medal came just 20 minutes later as Alex Gregory, George Nash, Moe Sbihi and Constantine Louloudis took victory in the men's four.
  Glover and Stanning are now unbeaten in 39 races, a run that stretches back five years.
  They became the first British female rowers to win an Olympic title when they won four years ago, but Stanning said Friday's victory in Rio eclipsed their London success.
  "This means so much more," she said. "We have been so emotional this week and it means so much to us."
  Glover added: "The pressure was immense. London was a home games and there was nothing more special but this is defending a title - it means so much."
  Find out how to get into rowing with our special guide.
  Glover and Stanning dominated from the start, building up a 3.58s lead at the halfway mark.
  New Zealand surged late on but the Britons had enough in hand to take victory.
  "I think they had another gear," said retired rower Sir Steve Redgrave, who won gold medals at five consecutive Olympic Games.
  "It is difficult to repeat what they did four years ago when they had a big lead because you have to keep going through the motions of it."
  Singer Pixie Lott: Yessssss golden girls!!!! You're amazing
  BBC presenter Dan Walker: Glover and Stanning have ripped this race to bits. What a performance. Solid gold... again
  Former world and European champion rower Polly Swann Amazing job by @Helenglovergb and Heather! So commanding. Double Olympic champions has a nice ring to it! Well done girls. Xx
target: Great Britain's Helen Glover and Heather Stanning successfully defended their Olympic title by winning gold in the women's pair at Rio 2016.