Gauff, 15, reached the Wimbledon main draw through qualifying then upset five-time champion Venus Williams in the first round before falling to eventual champion Simona Halep in the fourth round.
Gauff is joined by four other teenagers among eight wild-card invitees: a trio of 17-year-old Americans in Caty McNally, Whitney Osuigwe and Katie Volynets and 16-year-old French player Diane Parry.
Stosur brings a veteran presence. The Aussie, 35, won the title in Flushing Meadows in 2011 and has reached the quarters on two other occasions.
Other women’s wild cards went to former US collegiate champion Francesca di Lorenzo and three-time Stanford University All-American and New Jersey native Kristie Ahn.
On the men’s side, Americans Bjorn Fratangelo, Marcos Giron, Denis Kudla and Jack Sock join US Open Wild Card Challenge winner Ernesto Escobedo and 2019 US Tennis Association (USTA) Boys’ 18s National Champion Zachary Svajda as main-draw wild card recipients.
Antoine Hoang was awarded a main-draw wild card by the French Tennis Federation as part of its reciprocal agreement with the USTA, and Tennis Australia’s reciprocal agreement main-draw wild card will go to a player to be announced.