  Palomar Gattini-IR is a wide-field, synoptic infrared time domain survey
covering $\approx 15000$ sq. deg. of the sky at $\approx 1-3$ night cadence to
a depth of $J\approx 13.0$ and $\approx 14.9$ Vega mag in and outside the
Galactic plane, respectively. Here, we present the first data release of
$J$-band light curves of 2MASS sources within the survey footprint covering
approximately the first four years of operations. We describe the construction
of the source catalog based on the 2MASS point sources, followed by exposure
filtering criteria and forced PSF photometry. The catalog contains light curves
of $\approx 286$ million unique sources with 2MASS magnitudes of $J < 15.5$
mag, with a total of $\approx 50$ billion photometric measurements and $\approx
20$ billion individual source detections at signal-to-noise-ratio $> 3$. We
demonstrate the photometric fidelity of the catalog by i) quantifying the
magnitude-dependent accuracy and uncertainty of the photometry with respect to
2MASS and ii) comparing against forced PGIR aperture photometry for known
variable sources. We present simple filtering criteria for selecting reliable
photometric measurements as well as example Python notebooks for users. This
catalog is the largest compilation of nightly cadence, synoptic infrared light
curves to date, comparable to those in the largest optical surveys, providing a
stepping stone to upcoming infrared surveys in the coming decade.
