The 15-year-old American needed a lucky loser spot to get into the main draw but has taken her opportunity superbly, and a 7-6 (7-1) 6-4 victory over world No 8 Kiki Bertens gave her the biggest win, by ranking, of her early career.
The American, who will break into the top 100 as a result of her exploits in Austria, will face Andrea Petkovic on Saturday for a place in the final.
The teenage sensation secured a 6-4 6-4 victory to continue her phenomenal breakout year and become the youngest player to reach a WTA final since Czech Nicole Vaidisova in 2004.
Gauff said that while she is not bothered by juggling her tennis and school commitments, "sometimes I'm motivated and then I have moments when I don't want to do it (homework) at all".
"This is definitely unreal, my first final on the WTA", Gauff said after her win, according to Agence France-Presse.
Gauff is also in the doubles draw alongside her familiar partner Caty McNally.
'This is insane, I thought I was out of the tournament in qualifying, ' said the American.
"I'm thinking of the homework I have to do tonight". Andrea hit a lot of winners and put pressure on me.
The youngest-ever victor of a WTA Tour title was two-time US Open champion Tracy Austin, aged simply 14, at Portland in 1977.
Gauff beat Stefanie Voegele of Germany in the round of 32 after she stepped in as a lucky loser for injured sixth seed Maria Sakkari of Greece.
Now ranked 110th, Gauff showed real determination to save nine out of the 10 break points she faced, before she sealed victory on her second match point.