She beat both Venus Williams, and then Caroline Wozniacki en-route to the final, which she lost to Julia Gorges. Despite the loss, she had turned a number of heads, and went on to the WTA Premier tournament at Indian Wells in March as a wildcard.
She defeated three top 20 players including world No. 1 and two-time major champion Garbiñe Muguruza in straight sets to reach the semifinals.
There she beat world No. 6 Elina Svitolina in three sets and would play No. 8 Angelique Kerber in the final.
A tense final where Andreescu won the first, and dropped the second, culminated in a ripper final set which saw Andreescu pull through 6-4.
The victory vaulted her ranking to 24, a new career high.
At the WTA tournament in Toronto, Andreescu won her first four matches in straight sets, including the last two over top ten opponents in No. 5 Kiki Bertens and No. 3 Karolína Plíšková.
In advancing to a final, she spent 10 hours 54 minutes on court, the most of any player in the event.
In the final, she met Serena Williams, who experienced back spasms and was forced to retire at 3-1 down in the first set. This gave Andreescu her second WTA title, and a new career-high ranking of 14.
With the three top-ten wins she garnered at that tournament, she had won all seven matches against top-ten opponents to start her WTA career.
That would continue into the US Open, where she advanced to the semifinals by beating Katie Volynets, Kirsten Flipkens, Caroline Wozniacki, Taylor Townsend, and Elise Mertens.
She defeated Belinda Bencic in straight sets to reach her maiden Grand Slam final, where she would face Serena Williams.
Andreescu broke Williams in the very first game and led 5-3 with Williams serving to save the set. A double fault to handed Andreescu the first set 6-3.
She broke Williams again early in the second set to take a 2-love lead but Williams broke back to make it 2-1.
Andreescu immediately broke again to lead 3-1 and then held serve for 4-1 and broke again for 5-1.
All seemed lost for Williams with Andreescu serving for the match.
She had her first championship point at 40-30 which Williams saved to take it to deuce ... and then won the game to make it 5-2.
Williams then held for 5-3 and then incredibly broke again to love to make it 5-4, then held serve to level the set at 5-all.
Andreescu held for 6-5, and then led 40-15 on Williams serve for two championship points.
Williams saved the first, but could do nothing to stop Andreescu on the second.
She became the first woman to win the US Open in her debut appearance, the first teenager to win a Grand Slam singles title since Maria Sharapova won the 2006 US Open and the first player born in the 2000s to win a Grand Slam.
The win also propelled her to number five in the world on the WTA rankings where she ended the year.
Top 15 sporting moments of 2019
No 15 - Eliud Kipchoge's sub-two hour marathon
