Anthony Joshua served up a powerful performance to dispatch China's Beijing silver medallist Zhang Zhilei and become the fourth Great Britain fighter to guarantee a place on the podium with a 15-11 points win.
Watford-born Joshua, who boxes out of Finchley ABC, stalked his opponent from the start, pushing Zhang onto his back foot and setting the tempo with a big right hand, though the majority of shots from both men were failing to land in a tight and tentative opening spell.
The super heavyweight shaded the opener 3-1 on the scoreboard and his greater ambition served him well at the start of the second, a scoring right belatedly forcing the Chinese fighter to go on the offensive and begin to find some success with rights of his own.
For such an inexperienced top-level fighter, Joshua was staying admirably composed, and as the Chinese fighter started to open up with right hands the Londoner seized his chance to dump Zhang to the canvas with a sweeping right hand.
Scenting an early win, Joshua poured in hooks and rocked Zhang again, but in doing so opened himself up to dangerous counter shots as he extended his lead to four points heading into a raucous final round.
Zhang continued to look dangerous in the last, crashing home a big right as Joshua sought to stay on the back foot, and more hooks followed from Zhang but Joshua largely stayed out of danger to see out the final crucial seconds.
Joshua said: "My medal represents the hard work and the journey, but it's going to get tougher and I've just got to keep my head on my shoulders and try to change the colour of that medal.
"I learned so much from my first bout and I learned so much from this one too. I'm going to go away from these Olympics a new man because the experience is unbelievable - it's character-building.
"I'm not miles better than I was when I went to the World Championships, but I have improved. It's going to be a long career and I'll never stop improving until I finish, but I'm getting better bit by bit because of the experience."