The 22-year-old Puerto Rican, ranked 34th in the world, had never reached the last eight of a major tournament and arrived in Brazil completely under the radar.
Yet having reached the last four she defeated two-time Wimbledon champion Petra Kvitova of the Czech Republic, but was still a massive underdog going into the final against current world number two Kerber.
However, the form book was soon torn up. In an utterly fearless display, as she produced the tennis of her life, often forcing Kerber onto the back foot, as she pulled off a range of inspired ground stroke winners from all over the court.
The 22-year-old fell to the court and kissed it after sealing victory as fans waved Puerto Rican flags and yelled "Monica, Monica, Monica."
She broke down in tears on the podium. “It was the tournament, and greatest moment, of my life,” said Puig. “I wanted it so badly, I fought and my put my heart and soul on the court."
“I'm a pretty aggressive player .... I have that 'Boricua' fire in me," she added, using a common term for Puerto Rico and the country's inhabitants. “I know my country really wanted this victory,” she added.
World number 2 Kerber was full of praise for her opponent: “I think she came here with no pressure and I think she played one of the best weeks of her career,” said the German. “She had nothing to lose, she was going for it. I knew actually that she was a great player and at the end she deserved it. She played a really great week and beat a lot of top players.”
Bronze for Kvitova
Earlier in the day, Petra Kvitova defeated Madison Keys of the USA to win the bronze medal in three sets, 7-5 2-6 6-2. The Czech, who was in tears after the match, ranked her medal along side her Grand Slam triumphs. “The fact that I have a medal from the Olympics is one of the best things which happen in my career,” she said. “I have my two Wimbledon titles, Fed Cup and WTA. It's definitely one of the best days today so I hope I'm going to celebrate it. And I'm very proud I could bring it to the Czech Republic.”
On 14 August, attention switches to the men’s singles final where Great Britain’s Andy Murray attempts to mount the first ever successful defence of the title against Juan del Potro of Argentina.