Anax immaculifrons, the magnificent emperor, or blue darner, is a species of dragonfly in the family Aeshnidae. Almost all its range is in West and South Asia (the population further east in Asia is now recognized as a separate species, A. aurantiacus); it is Europe's largest dragonfly but very marginal in the continent where restricted to some Aegean Islands and Cyprus.
A. immaculifrons has a length of and a wingspan of about . It is a large, bluish green dragonfly with sapphire-blue eyes, bluish-green thorax, and pale reddish-brown abdomen marked with black. Its thorax is pale bluish-green on dorsum with a blackish-brown mid-dorsal carina and turquoise-blue laterally. There is a narrow black stripe over humeral suture and a very broad one over the postero-lateral suture with a narrow black posterior border on metepimeron. Wings are transparent with amber-yellow tint. Segment 1 of the abdomen is entirely black. Segment 2 is turquoise-blue, with a mid-dorsal transverse mark shaped like a sea-gull in flight. Segment 3 has its basal half turquoise-blue and apical half black, with a small mid-dorsal spot on blue. Segments 4 to 8 are with apical half black and pale reddish-brown at base. Segment 9 and 10 are black on dorsum. A more reddish form from southeast Asia and southern China was formerly included in this species, but in 2022 it was recognized as a separate species, A. aurantiacus.
A. immaculifrons is found near slow flowing hill or mountain streams where it breeds. Eggs are inserted into reeds emerging from water.