  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 soon after the planetary signal.
The duration of the planetary signal is $\sim 2.5\,$hours. The measured ratio
of the planet mass to its host star is $q = 4.2\pm 0.7 \times10^{-5}$. 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.
