The performance of line-focus concentrating solar power (CSP) systems, operating at concentrations <100 suns, is limited by receiver thermal losses. Existing linear CSP receivers rely on spectrally selective surfaces enclosed within cylindrical vacuum tubes to minimize heat loss due to radiation and convection. However, using spectrally selective coatings and maintaining a high-quality vacuum at high temperatures (up to 400 °C) increases cost, reduces durability, and restricts receiver geometry to a cylindrical shape. We have developed a solar thermal aerogel receiver comprising of custom-fabricated highly-transparent thermally-insulating silica aerogels that allow transmission of concentrated sunlight, minimization of thermal losses and enables operation in air. We demonstrate the on-sun performance of the prototype aerogel receiver with a 1 m×10 cm aperture area. The prototype receiver consists of seven monolithic solar-transparent aerogel tiles that cover the solar-absorber consisting of a piping loop connected in series and coated with black Pyromark paint. The receiver is paired with a 6 m×6 m linear Fresnel reflector (LFR) array capable of achieving concentration up to 30 suns. Pressurized Dowtherm A is used as the heat transfer fluid which is heated to temperatures up to 350 °C before entering the receiver section. We performed on-sun measurements for different receiver inlet temperatures and incident flux conditions, and report a peak receiver thermal efficiency >65%.