Since Election Day on Wednesday, Mr Trump has used Twitter to air false claims of voter fraud and to claim victory in several key battleground states where votes are still being counted.
The 17-year-old climate change activist has famously clashed with the 74-year-old president in the past, with Trump taking to his own Twitter account last year to ridicule her Time Magazine cover, writing: "So ridiculous".
On Thursday, Greta Thunberg tweeted, "So ridiculous".
As it stands, Thunberg had to wait exactly 11 months to give Donald Trump the flawless clap back.
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McSally's failed 2018 election contest against Democratic Senator Kyrsten Sinema took six days to produce a victor . Cheri Bustos, who chairs the Democratic Congressional Campaign Committee, to be ousted from her job.
Mr Trump won in-person votes in larger numbers.
However, Thunberg wasn't the only person giving Trump an ironic jab on Thursday. Using Trump's 2019 tweet as a template, Greta tweeted, "Chill Donald, Chill!".
Ms. Thunberg's quick reaction to Mr. Trump's tweet came as the USA formally exited from the Paris climate agreement on Wednesday. The message harkens back to an infamous guerrilla ad for a local band in the 1990s that in turn referenced a scene at the end of the 1939 film "The Wizard of Oz", in which "Surrender Dorothy" is written in the sky by the Wicked Witch of the West, the film's primary antagonist.
The president's criticisms of her at the time drew widespread criticism as being patronising.
Ms. Thunberg has become a leading global voice for action on climate change, inspiring millions of students to join protests around the world.
Politicians have mostly praised Thunberg and her movement as an important voice of her generation.