Coco Gauff has become the youngest player since Maria Sharapova in 2005 to qualify for the WTA Finals in singles.
The 18-year-old has also achieved the rare feat of qualifying for the season-ending finals in both singles and doubles, with partner Jessica Pegula.
Gauff and Pegula will be the first Americans to play at the WTA Finals in singles and doubles since Serena and Venus Williams in 2009.
Gauff sealed her place by reaching the third round of the Guadalajara Open.
The WTA Finals take place in Fort Worth, Texas, from 31 October-7 November.
"It means a lot," said world number seven Gauff, who beat Elisabetta Cocciaretto 7-6 (7-1) 6-3.