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We request deep near-infrared imaging of an SPT-selected protocluster comma SPT0311-62 located at z=6.9. It possesses a very large virgul10elev13 Msun halo mass for any structure at z>4 comma immense at zvirgul7. Selected via millimeter-wavelength dust emission in the 2500 square degree South Pole Telescope (SPT) survey comma it has been resolved by ALMA into 11 gas-rich galaxies comma the 6 brightest -most massive confirmed spectrally to lie in an extended protocluster. Sensitive observations of carbon monoxide and ionized carbon with ALMA comma allow assessment of the obscured star formation and gas masses of bright cluster members. The goal of this proposal is to obtain F160W comma F125W comma F814W HST imaging (3 tiled pointings in WFC3 comma 1 pointing ACS) to measure the stellar properties comma galaxy morphologies comma and assess the spatial extent of these structures. The proposed HST observations will provide the imaging and photometric information required for a complete picture of the obscured and unobscured stellar components of the ALMA galaxies comma and the expected overdensity of LBGs comma revealing the complicated structure in the gas-rich galaxies that host rapid star formation and the less luminous galaxies which trace the filaments of an early collapsing structure. The combination of high resolution ALMA datasets with the proposed HST observations will allow a full characterization of the stars comma gas comma and dust in this cosmologically important protocluster of primordial starburst galaxies comma well into the epoch of reionization in the Universe. From an outreach perspective comma the high spatial resolution of the HST identifications of protocluster galaxies will complement the ALMA data in publicizing these high impact results.