  We present multiwavelength photometric catalogues (HST, Spitzer and Hawk-I K
band) for the first two of the Frontier Fields, Abell2744 and MACSJ0416 (plus
their parallel fields). To detect faint sources even in the central regions of
the clusters, we develop a robust and repeatable procedure that uses the public
codes Galapagos and Galfit to model and remove most of the light contribution
from both the brightest cluster members as well as the ICL. We perform the
detection on the HST H160 processed image to obtain a pure H-selected sample.
We also add a sample of sources which are undetected in the H160 image but
appear on a stacked infrared image. Photometry in the other HST bands is
obtained using SExtractor, performed again on residual images after the Galfit
procedure for foreground light removal. Photometry on the Hawk-I and IRAC bands
has been obtained using our PSF-matching deconfusion code T-PHOT. A similar
procedure, but without the need for the foreground light removal, is adopted
for the Parallel fields. The procedure allows for the detection and the
photometric measurements of ~2500 sources per field. We deliver and release
complete photometric H-detected catalogues, with the addition of a
complementary sample of infrared-detected sources. All objects have
multiwavelength coverage including B to H HST bands, plus K band from Hawk-I,
and 3.6 - 4.5 {\mu}m from Spitzer. Full and detailed treatment of photometric
errors is included. We perform basic sanity checks on the reliability of our
results. The multiwavelength catalogues are publicly available and are ready to
be used for scientific purposes. Our procedures allows for the detection of
outshined objects near the bright galaxies, which, coupled with the
magnification effect of the clusters, can reveal extremely faint high redshift
sources. Full analysis on photometric redshifts is presented in a companion
Paper II. [abridged]
