This attractive soldier fly (9 mm) has sexes that are very different in appearance. 
Both have a shiny green thorax but the female has a blue-green abdomen, sometimes with a violet sheen, and the male has a bronze abdomen. 
The eyes are covered in dense black hairs, which helps to distinguish it from the similar soldier flies within the genus Sargus, like Sargus bipunctatus.

1st photo: A female (eyes are not touching each other)
2nd photo: A male (eyes are touching each other)

Gagelpolder, Utrecht, The Netherlands, 30 June 2021