The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling), is a unit of length in the International System of Units (SI), equal to one billionth (short scale) or one thousand million (long scale) of a meter (0.000000001 m) and to 1000 picometres.

[1][2][3] The name combines the SI prefix nano- (from the Ancient Greek νάνος, nanos, "dwarf") with the parent unit name metre (from Greek μέτρον, metron, "unit of measurement").

The nanometre is also commonly used to specify the wavelength of electromagnetic radiation near the visible part of the spectrum: visible light ranges from around 400 to 700 nm.

Since the late 1980s, in usages such as the 32 nm and the 22 nm semiconductor node, it has also been used to describe typical feature sizes in successive generations of the ITRS Roadmap for miniaturized semiconductor device fabrication in the semiconductor industry.

The CJK Compatibility block in Unicode has the symbol U+339A ㎚ SQUARE NM.