Sinner is the only top-four player left in the men's draw following the exits of Novak Djokovic, Carlos Alcaraz and Alexander Zverev.
The world number one now has five Grand Slam titles to her name.
The world number one is just one match away from becoming the first woman to win the tournament in three straight years since Justine Henin in 2007 after a 6-2, 6-4 victory.
Swiatek wrapped up victory after nearly three hours.
In front of a packed centre court crowd Swiatek won her 36th match of the year and became the first woman since Serena Williams in 2013 to win at Madrid and Rome in the same season.
Coming back from 1-3 down in the decider and saving three match points in total, Swiatek claimed a 7-5, 4-6, 7-6 (9/7) victory to secure the Madrid Open trophy for the first time.
On the women's side, Iga Swiatek was made to sweat in her 4-6, 6-0, 6-2 victory over Brazilian lefty Beatriz Haddad Maia, as she dropped her first set of the tournament and needed two and a half hours to reach a second consecutive Madrid semi-final.
Zendaya and boyfriend and fellow actor Tom Holland were among the crowd Sunday as Poland's Swiatek beat Maria Sakkari 6-4, 6-0 to win the prestigious Indian Wells WTA title for the second time.
"Really happy, it's not easy to play the first match, especially the first Grand Slam of the season," said Swiatek, who owns three Roland Garros crowns and another at the US Open.
Sinner is the only top-four player left in the men's draw following the exits of Novak Djokovic, Carlos Alcaraz and Alexander Zverev.
The world number one now has five Grand Slam titles to her name.
The world number one is just one match away from becoming the first woman to win the tournament in three straight years since Justine Henin in 2007 after a 6-2, 6-4 victory.
Swiatek wrapped up victory after nearly three hours.
In front of a packed centre court crowd Swiatek won her 36th match of the year and became the first woman since Serena Williams in 2013 to win at Madrid and Rome in the same season.
Coming back from 1-3 down in the decider and saving three match points in total, Swiatek claimed a 7-5, 4-6, 7-6 (9/7) victory to secure the Madrid Open trophy for the first time.
On the women's side, Iga Swiatek was made to sweat in her 4-6, 6-0, 6-2 victory over Brazilian lefty Beatriz Haddad Maia, as she dropped her first set of the tournament and needed two and a half hours to reach a second consecutive Madrid semi-final.
Zendaya and boyfriend and fellow actor Tom Holland were among the crowd Sunday as Poland's Swiatek beat Maria Sakkari 6-4, 6-0 to win the prestigious Indian Wells WTA title for the second time.
"Really happy, it's not easy to play the first match, especially the first Grand Slam of the season," said Swiatek, who owns three Roland Garros crowns and another at the US Open.
Swiatek, whose grip on top spot is under threat from Aryna Sabalenka in New York, needed just 58 minutes to dispose of the 86th-ranked Peterson.