Nickel arsenide is a compound of nickel and arsenic and component of the ore nickeline. It is highly toxic^{[citation needed]} and a known carcinogen in humans. Uncontrolled decomposition of nickel arsenide can give rise to further toxic nickel compounds.^{[citation needed]}

Nickel arsenide was one of the first compounds that revealed the toxicity of nickel. The damage to the miners' lungs was documented by Georgius Agricola in the 16th century: "kupfer-nickel" ores in the Schneeberg mines contained red-colored NiAs mineral originally mistaken for the copper ore, thus the German: kupfer (copper) in the name. The German: Nickel (demon) name was reflecting the damage it did to the health of the workers, in addition to them being unable to extract any copper from this ore.

The acute oral LD50 in rats is about 6000 mg/kg.

The main compound within nickeline, nickel arsenide (NiAs), can be prepared by direct combination of the elements:

Ni(s) + As(s) → NiAs(s)