We report on the first detection of X-ray dust scattered rings from the Galactic low mass X-ray binary V404 Cyg \xspace .
The observation of the system with Swift \xspace /XRT on June 30 2015 revealed the presence of five concentric ring-like structures centred at the position of V404 Cyg \xspace .
Follow-up Swift \xspace /XRT observations allowed a time-dependent study of the X-ray rings .
Assuming that these are the result of small-angle , single X-ray scattering by dust grains along the line of sight , we find that their angular size scales as \theta \propto \sqrt { t } in agreement with theoretical predictions .
The dust grains are concentrated in five dust layers located at about 2.12 , 2.05 , 1.63 , 1.50 and 1.18 kpc from the observer .
These coincide roughly with locations of enhanced extinction as determined by infrared photometry .
Assuming that the grain size distribution is described by a generalized Mathis-Rumpl-Nordsieck model , we find that the power-law index of the most distant cloud is q \sim 4.4 , while q \sim 3.5 - 3.7 in all other clouds .
We constrain at a 3 \sigma level the maximum grain size of the intermediate dust layers in the range 0.16 - 0.20 \mu m and set a lower limit of \sim 0.2 \mu m in the other clouds .
Hints of an exponential cutoff at the angular intensity profile of the outermost X-ray ring suggest that the smallest grains have sizes 0.01 \mu { m } \leq \alpha _ { \min } \lesssim 0.03 \mu m. Based on the relative ratios of dust column densities we find the highest dust concentration at \sim 1.6 kpc .
Our results indicate a gradient in the dust properties within 1 kpc from V404 Cyg \xspace .