Miroslaw had been the clear favourite after breaking her own world record twice in the lead-up to the finals, climbing the 15-metre wall in 6.06 seconds two days ago.
At the Le Bourget venue on Wednesday, she did the vertical run in 6.10 seconds, beating China's Deng Lijuan in a photo finish. The silver medallist set her personal best in the race, with 6.18s.
"It means a lot," Miroslaw said. "It's the first time for speed climbing and... I have my flag, and I was standing on the podium in the first place (position) hearing the national anthem. It was amazing."
Her compatriot Aleksandra Kalucka won the bronze medal with a time of 6.53s.
Sport climbing is making its second Olympic appearance but the Paris Games are the first where the speed discipline is a separate medal event from boulder and lead, as is the norm for the sport due to the vastly different techniques required.
The smallest misstep can seal the fate of athletes in the Olympics' fastest race, as it did for American Emma Hunt.
In arguably the day's biggest upset, Hunt was eliminated in the quarter-finals after her right foot slipped halfway up the wall. The 21-year-old had been the favourite to challenge Miroslaw for the gold.
Earlier, the men's lead semi-finals determined the final eight athletes to vie for gold in the combined boulder and lead competition on Friday. The scores from the two stages were added up to determine the finalists.
Japan's rising star Sorato Anraku sailed through at the top of the leaderboard after the 17-year-old had racked up a massive surplus in the boulder stage.
He climbed fourth from the top in the lead event, in which athletes are given six minutes to climb a steep, 15-metre structure as high as possible in a single attempt.
His compatriot Tomoa Narasaki failed to make the final.
Despite coming in second behind Anraku in boulder, the twice-Olympian fell on a tricky low section of the route when he went for a high-risk move, losing a shot at redemption after just missing the podium in Tokyo.
Narasaki's slip-up meant Britain were the only country to get both of their climbers in the final with Hamish McArthur sneaking through to join 19-year-old Toby Roberts.