We report discovery of the lowest mass ratio exoplanet to be found by the microlensing method in the light curve of the event OGLE 2016–BLG–1195 .
This planet revealed itself as a small deviation from a microlensing single lens profile from an examination of the survey data .
The duration of the planetary signal is \sim 2.5 hours .
The measured ratio of the planet mass to its host star is q = 4.2 \pm 0.7 \times 10 ^ { -5 } .
We further estimate that the lens system is likely to comprise a cold \sim 3 Earth mass planet in a \sim 2 AU wide orbit around a 0.2 Solar mass star at an overall distance of 7.1 kpc .