Abstract: A magnesium based alloy for high pressure die casting, comprising at least 83 wt % magnesium; 4.5 to 10 wt % Al; wt % Zn that is comprised in one of the two ranges 0.01 to 1 and 5 to 10; 0.15 to 1.0 wt % Mn; 0.05 to 1 wt % of rare earth elements; 0.01 to 0.2 wt % Sr; 0.0005 to 0.0015 wt % Be; and calcium in an amount higher than 0.3 (wt % Al -4.0).sup.0.5 wt % and lower than 1.2 wt %. The alloy may further comprise incidental impurities. The alloy may comprise at least 88 wt % magnesium, 4.5 to 10 wt % Al, 0.1 to 1 wt % of rare earth elements. The alloy may contain 5 to 10 wt % Zn and 0.1 to 1 wt % of rare earth elements, and wherein the zinc content is related to the aluminum content by the formula: wt % Zn=8.2-2.2 in (wt % Al -3.5).