Hwang had vowed to win gold in London after managing only a bronze at the world championships in Korea last year, and the 26-year-old enjoyed a comfortable 12-5 win over European champion Tatar to deliver South Korea's 13th gold medal of the Games.
That tally ties the overall record medal haul Korea set in Beijing four years ago, and with Cha Dong-min and Lee In-jong set to compete in the heavyweight categories on Saturday they could soon surpass that mark.
Hwang was in tears after her victory and said she was so proud to have won another gold in the Korean martial art.
"It feels like flying," she said.
"It's very precious for me personally and for the country. I've done something special for the country and it makes me very proud."
American Paige McPherson and Helena Fromm of Germany won bronze medals through the repechage competition.
A day after Jade Jones had earned Britain's first taekwondo gold medal, Sarah Stevenson failed to reproduce the kind of form that got her bronze in Beijing, losing to American McPherson in the first round.
Argentina's Sebastian Eduardo Crismanich won the men's welterweight taekwondo gold medal by beating Nicolas Garcia Hemme of Spain in the final.
Crismanich, who won the Pan American qualifiers for London, beat Hemme 1-0 in a cagey final to win Argentina's first Olympic taekwondo medal. He scored the deciding point with seconds remaining then survived an onslaught to seal the gold.
"I can't express with words what I feel and what is happening to me," he said. "It's a dream. I am really happy."
Britain's Lutalo Muhammad, controversially selected in place of world number one Aaron Cook, lost to Hemme in the quarter-finals but made it through the repechage competition to the bronze medal match, where he faced Armenia's Armen Yeremyan.
The Londoner's power and range of kicks earned him a 9-3 win and gave Britain's men their first Olympic medal in taekwondo.
Italy's Mauro Sarmiento took the other bronze.