  We present the first results of the Hubble Deep Hydrogen Alpha (HDH$\alpha$)
project, which analyzes the space-borne deep H$\alpha$ narrowband imaging data
in the GOODS-S region. The HDH$\alpha$ data comprises 72 orbits' images taken
with the HST ACS/WFC F658N filter. The exposure time varies across a total area
of $\sim$76.1 $\rm{arcmin}^2$, adding up to a total exposure time of 195.7 ks,
among which 68.8 ks are spent in the deepest region. These images are aligned,
reprojected, and combined to have the same pixel grid as the Hubble Legacy
Fields (HLF). The scientific goals of the HDH$\alpha$ include establishing a
sample of emission-line galaxies (ELGs) including [O III] emitters at $z\sim$
0.3, [O II] emitters at $z\sim$ 0.8, and Lyman-$\alpha$ emitters (LAEs) at $z
\sim 4.4$, studying the line morphology of ELGs with high resolution imaging
data, and statistically analyzing the line luminosity functions and line
equivalent-width distributions of ELGs selected with HST. Furthermore, the
HDH$\alpha$ project enhances the legacy value of the GOODS-S field by
contributing the first HST-based narrowband image to the existing data sets,
which includes the HST broadband data and other ancillary data from X-ray to
radio taken by other facilities. In this paper, we describe the data reduction
process of the HDH$\alpha$, select ELGs based on HST's F658N and broadband
data, validate the redshifts of the selected candidates by cross matching with
the public spectroscopic catalogs in the GOODS-S, and present a final catalog
of the confirmed [O III] emitters at $z\sim$ 0.3, [O II] emitters at $z\sim$
0.8, and LAEs at $z \sim 4.4$.
