Ben Whittaker edged into the men’s light-heavyweight final with a split decision verdict over Imam Khataev of the Russian Olympic Committee.
The 24-year-old from Wolverhampton becomes the second British boxer to book his final place after Pat McCormack’s bye earlier on Sunday.
Lauren Price is already guaranteed at least a bronze medal, while Karriss Artingstall will take home bronze in the women’s featherweight division.
McCormack will fight for men’s welterweight gold after his semi-final opponent Aidan Walsh was forced to withdraw due to injury.
The Irish fighter sustained an ankle injury during his quarter-final win over Merven Clair of Mauritius on Friday and has been ruled out following a scan.
McCormack, who had been scheduled to face Walsh at lunchtime on Sunday, will go straight through to face either Russia’s Andrey Zamkovoy or Roniel Iglesias of Cuba in Tuesday’s final, while Walsh must settle for bronze.
The Olympic Federation of Ireland said in a statement: “The decision has been made to withdraw Aidan Walsh from the semi-final of the men’s welterweight competition at the Olympic Games.
“The Belfast boxer was due to fight in Sunday’s semi-final against Pat McCormack, but due to an ankle injury sustained during his quarter-final bout with Mervin Clair, the decision to withdraw him was made in conjunction with his medical team.
“Walsh had initially hoped to compete and waited to give himself every opportunity to do so. However subsequent scans and medical reviews have now ruled out this possibility.”
Walsh emerged as a surprise medal contender for Ireland having admitted he almost quit the sport after failing to make the team for the Rio Olympics.
Ireland’s boxing team leader Bernard Dunne said: “What Aidan did this week is an incredible achievement.
“His performance throughout the tournament has been outstanding, and it is great to see him write his name in the annals of Irish sport.”