The unseeded Polish teenager overpowered the fourth-seeded American 6-4, 6-1 in their women's singles championship match in Paris.
Świątek did not lose a set on her way to the title.
The victory at Roland Garros marked a new career milestone for the Polish 19-year-old, who is a former junior Wimbledon champion.
She went into the tournament ranked world No. 54 by the Women's Tennis Association (WTA).
Świątek reached the semifinals of the women’s doubles competition at this year's French Open together with Nicole Melichar of the United States.
The two failed to make the final after losing 6-7, 6-1, 4-6 to the pairing of Chilean Alexa Guarachi and American Desirae Krawczyk on Friday.
(gs)
Source: Eurosport, PAP