The black spine-neck swamp turtle (Acanthochelys spixii), also commonly known as the spiny-neck turtle or Spix's sideneck turtle, is a species of turtle in the family Chelidae. The species is endemic to South America, specially in the Southern Cone region.
The specific name, spixii, is in honor of German biologist Johann Baptist von Spix.
A. spixii is found in Argentina, Brazil, Uruguay, and possibly Paraguay.