Magnesium alloy and magnesium-air battery -

The purpose of the present invention is to provide a magnesium-lithium alloy suitable for use in the negative electrode of an air battery, a negative electrode using said alloy, and a magnesium air battery. This magnesium-lithium alloy comprises greater than 10.50 mass% and less than or equal to 19.50 mass% of Li, 0-15.00 mass% of Al, 0-5.00 mass% of Ca, 0-3.00 mass% of Zn, 0-3.00 mass% of R, 0-2.00 mass% of Mn, 0-0.10 mass% of Fe, 0-0.10 mass% of Cu, 0-0.10 mass% of Ni, with the remainder being Mg and unavoidable impurities, wherein R represents one or more rare earth elements selected from Y, La, Ce, Nd and Gd.