Champions go for gold in Super Saturday title defence
Britain is hoping for a repeat of Super Saturday from the London 2012 Olympics as track and field champions Greg Rutherford, Mo Farah and Jessica Ennis-Hill try to defend their titles.
Veteran rowers Pete Reed, 35, and Andrew Triggs Hodge, 37, are going after gold number three in the men's eight at 3:27pm following triumphs at Beijing 2008 and London 2012 in the coxless four.
Laura Trott, 24, is looking for her third gold medal in cycling after a stunning debut Olympics in 2012 where she came first in the omnium and team pursuit events.
Rutherford, 29, will be the first in action when the men's long jump takes place at Rio's Olympic stadium at 00:53am on Sunday.
Rutherford, of Milton Keynes, the world, European and Commonwealth champion, said his personal inspiration would come from a video of his 21-month-old son Milo jumping up and down with a Union flag in his hand saying he is cheering for Daddy and Team GB.
Rutherford tweeted: "One of the best videos ever!! I miss my boy like mad and I'll be watching this just before I set off into the stadium."
Farah, 33, who competes in the 10,000 metres, is beginning his campaign to seal his place as one of the greats of athletics by winning the double-double with victories in the 5,000m and 10,000m.
Only one man, the Flying Finn, Lasse Viren, has successfully defended an Olympic 5,000m and 10,000m track double.
With no heats, every runner has just one chance in the unforgiving final, which starts at 1:27am.
Sheffield star athlete Ennis-Hill, 30, is going for gold in the heptathlon but her plans could be scuppered by British rival Katarina Mary Johnson-Thompson, 23, of Liverpool, Canada's Brianne Theisen-Eaton and Belgium's Nafissatou Thiam.
Johnson-Thompson had a strong showing on the first day of the seven-event competition, even breaking the British record in the high jump.
Four of the seven events were completed on Friday and Ennis-Hill is in first place 72 points clear of her nearest challenger, with compatriot Johnson-Thompson in fourth.
Cyclist Laura Trott takes to the velodrome at 3:34pm in the women's team pursuit alongside Ciara Horne, Elinor Barker, Katie Archibald and Joanna Rowsell-Shand. The gold medal race is scheduled for 9:14pm.
The team posted a world record time in qualification of 4:13.26 minutes on Thursday.
In the rowing final Reed and Triggs Hodge are joined by Matthew Langridge, Matt Gotrel, Will Satch, Tom Ransley, Scott Durant, Paul Bennett and cox Phelan Hill. The team posted the fastest time in the heats of 5:34.23 minutes as they look for the first gold medal in the event since 2000.
The women's eight also go for gold in their final, 20 minutes before the men at Lagoa Stadium at 3:07pm.
Boxing super heavyweight Joe Joyce, 30, get his maiden Olympics under way at 11pm in the preliminaries. The 6ft 6ins, 17 stone boxer is the reigning Commonwealth champion and faces Davilson dos Santos Morais of Cape Verde. He will look to emulate London 2012 gold medallist Anthony Joshua.