  Radio and $\gamma$-ray loud narrow-line Seyfert 1 galaxies (NLS1s) are unique
objects to study the formation and evolution of relativistic jets, as they are
believed to have high accretion rates and powered by low mass black holes
contrary to that known for blazars. However, only about a dozen $\gamma$-ray
detected NLS1s ($\gamma$-NLS1s) are known to date and all of them are at
$z\le1$. Here, we report the identification of a new $\gamma$-ray emitting NLS1
TXS 1206+549 at $z=1.344$. A near-infrared spectrum taken with the Subaru
telescope showed H$\beta$ emission line with FWHM of $1194\pm77$ km s$^{-1}$
and weak [O III] emission line but no optical Fe II lines, due to the limited
wavelength coverage and poor signal-to-noise ratio. However, UV Fe II lines are
present in the SDSS optical spectrum. The source is very radio-loud,
unresolved, and has a flat radio spectrum. The broadband SED of the source has
the typical two hump structure shown by blazars and other $\gamma$-NLS1s. The
source exhibits strong variability at all wavelengths such as the optical,
infrared, and $\gamma$-ray bands. All these observed characteristics show that
TXS 1206+549 is the most distant $\gamma$-NLS1 known to date.
