Neptunium silicide is a binary inorganic compound of neptunium and silicon with the chemical formula NpSi2.

[1] The compound forms crystals and does not dissolve in water.

[2] Heating neptunium trifluoride with powdered silicon in vacuum:[3] Neptunium silicide forms crystals[4] of tetragonal crystal system, space group I41/amd, cell parameters: a = 0.396 nm, c = 1.367 nm, Z = 4.

[5] Neptunium disilicide does not dissolve in water.

Neptunium disilicide reacts with HCl:[3]