The Ly extgreek{a} Reference Sample (LARS) is a substantial program with the Hubble Space Telescope ( HST )

that provides a sample of local universe laboratory galaxies in which to study the detailed

astrophysics of the visibility and strength of the Ly extgreek{a}line of neutral hydrogen. Ly extgreek{a} is the dominant

spectral line in use for characterizing high-redshift ( z ) galaxies. This paper presents an

overview of the survey, its selection function, and HST imaging observations. The sample was

selected from the combined GALEX +Sloan Digital Sky Survey catalog at z = 0.028-0.19, in order to

allow Ly extgreek{a} to be captured with combinations of long-pass filters in the Solar Blind Channel (SBC) of

the Advanced Camera for Surveys (ACS) onboard HST . In addition, LARS utilizes H extgreek{a} and H extgreek{b} narrowband

and u , b , i broadband imaging with ACS and the Wide Field Camera 3 (WFC3). In order to study

galaxies in which large numbers of Ly extgreek{a} photons are produced (whether or not they escape), we

demanded an H extgreek{a} equivalent width W (H extgreek{a}) $geq$100 {AA}. The final sample of 14 galaxies covers far-UV (FUV, extgreek{l}

{~} 1500~{AA}) luminosities that overlap with those of high- z Ly extgreek{a} emitters (LAEs) and Lyman break

galaxies (LBGs), making LARS a valid comparison sample. We present the reduction steps used to

obtain the Ly extgreek{a} images, including our LARS eXtraction software (LaXs), which utilizes pixel-by-pixel

spectral synthesis fitting of the energy distribution to determine and subtract the continuum at

Ly extgreek{a}. We demonstrate that the use of SBC long-pass-filter combinations increase the signal-to-noise

ratio by an order of magnitude compared to the nominal Ly extgreek{a} filter available in SBC. To exemplify the

science potential of LARS, we also present some first results for a single galaxy, Mrk~259

(LARS~{#}1). This irregular galaxy shows bright and extended (indicative of resonance scattering) but

strongly asymmetric Ly extgreek{a} emission. Spectroscopy from the Cosmic Origins Spectrograph on board HST

centered on the brightest UV knot shows a moderate outflow in the neutral interstellar medium

(probed by low ionization stage absorption features) and Ly extgreek{a} emission with an asymmetric profile.

Radiative transfer modeling is able to reproduce the essential features of the Ly extgreek{a} line profile and

confirms the presence of an outflow. From the integrated photometry we measure an Ly extgreek{a} luminosity of

L Ly extgreek{a} =1.3 $ imes$ 10 42~erg s --1 an equivalent width W (Ly extgreek{a}) = 45~{AA} and an FUV absolute magnitude M FUV =

--19.2 (AB). Mrk~259 would hence be detectable in high- z Ly extgreek{a} and LBG surveys. The total Ly extgreek{a} escape

fraction is 12{%}. This number is higher than the low- z average, but similar to that at z { extgreater} 4,

demonstrating that LARS provides a valid comparison sample for high- z galaxy studies.