Vince, a four-year-old white rhino, was shot three times in the head on Monday night at the rhinoceros enclosure at Thoiry zoo, situated at the back of the compound's African Animal Park Reserve.
Zoo keepers only made the macabre discovery of the dead white rhino, which had been a resident since 2015, on Tuesday morning.
Thoiry zoo described the attack as a 'heinous act' on its Facebook page.
“Vince was found this morning by his carer who, very attached to animals, is deeply affected," it wrote.
“This heinous act was carried out despite the presence of five members of the zoological staff living on site and surveillance cameras.”
It added: “The other two white rhino living in Thoiry, Gracie 37 years old and Bruno 5 years of age, have escaped the massacre and are safe and sound."
Thierry Duquet, the zoo director, said that the "extremely shocking" attack was a first in Europe.
"The criminals broke several security systems.They shot Vince dead and cut off one of his horns, probably with a chainsaw."
"His second horn was only partially cut, which suggests that the criminals were interrupted or that their material was defective."
There are around 21,000 white rhinos in the world, with those in the wild mainly living in South Africa and Uganda, but the species is under threat from poaching.
The white rhino is particularly vulnerable, because it is generally not aggressive and has poor eye-sight.
Rhino horns are highly prized in traditional Asian medicine for their alleged qualities as an aphrodisiac, and are ground into a fine powder or compacted into tablets to treat various conditions, including loss of libido.
Rhinoceros horns can fetch up to £180,000 on the black market.
The bulk of horns are poached in South Africa, which saw 1,175 rhinos killed for their ivory in 2015 alone.
There have been cases of horns swiped from stuffed animals before, but this is the first known case in Europe of one being killed for its ivory in a zoo.
A criminal inquiry has been launched.