The newly discovered insect was named Nelloptodes gretae after the 16-year-old Swedish activist, according to the Natural History Museum in London.
"I'm really a great fan of Greta," Michael Darby, who works at the museum and named the insect, said in a statement. "She is a great advocate for saving the planet and she is amazing at doing it, so I thought that this was a good opportunity to recognize that."
Nelloptodes gretae is described as a yellow and gold beetle, with no eyes or wings, that measures just 0.79 millimeters. The beetle's small size is one of the reasons it had been so unknown.
"They are even dwarfed by some unicellular organisms," according to the museum.
The bug was first collected in Kenya between 1964 and 1965 by entomologist William Brock. He took samples of soil from around east Africa and gave them to the museum, where they had been stored away up until now.
Darby went through the samples recently and was able to describe Nelloptodes gretae, as well as a new genus and eight other new beetle species.
Thunberg recently made headlines for her damning speech at the U.N. Climate Action Summit, in which she condemned world leaders.