We report the synthesis, crystal structure, and magnetic properties of Co₃(OH)₄(ethanedisulfonate), a layered cobalt hydroxide pillared by ethanedisulfonate ligands (P2₁/c, a = 8.9462(6) Å, b = 5.2818(4) Å, c = 10.1259(7) Å, β = 93.297(2)°, V = 477.68(6) ų, Z = 2). The structure displays two-dimensional infinite Co–O–Co connectivity, with the octahedra forming what we believe is a novel M₃X₈ inorganic layer topology; brucite-like ribbons of edge-sharing octahedra share corners with other ribbons along a second direction to form perforated layers of octahedra. Magnetic measurements reveal a sharp peak in susceptibility at 38 K, with a Curie–Weiss constant of −243 K and an effective magnetic moment (µ_eff) of 4.35 µ_B per Co. A field-induced transition from a triangular antiferromagnetic to a collinear ferrimagnetic state occurs in high fields. Heat capacity measurements indicate a relatively small magnetic entropy change, suggesting that the magnetic ordering is only two-dimensional. Thermogravimetric analysis and differential thermal analysis of the material show stability to 350 °C.