The US company will get $2.5 billion in cash and become the largest shareholder in Adevinta, with a 44% equity stake and a third of the voting rights.
The combined company will have classified ad websites in 20 countries, covering a billion people and receiving about three billion monthly visits.
“With the acquisition of eBay Classifieds Group, Adevinta becomes the largest online classifieds company globally, with a unique portfolio of leading marketplace brands,” Adevinta chief executive Rolv Erik Ryssdal said.
EBay’s classified brands include Gumtree, Marktplaats in the Netherlands, Mobile.de in Germany, Vivanuncios in Mexico and Canada’s Kijii.
Adevinta owns Leboncoin, France’s biggest online classifieds site, and classified businesses in more than a dozen other countries in Europe, North Africa and Latin America.
It was spun off last year from Norwegian media company Schibsted.