Abstract: A focussing solar collector is described including a solar-radiation reflector and a solar-radiation absorber disposed to receive the solar-radiations directly and those reflected from the reflector, characterized in that the reflector is of a cylindrical configuration having a semi-circular cross-section of constant radius of curvature, and that the absorber is of flattened cross-section having a height of from 0.1 to 0.5 times the radius of curvature of the reflector and a width substantially less than its height, the absorber being disposed within the reflector with one end of the absorber at the mid-point of the reflector inner surface and with the height axis of the absorber aligned with the reflector radius from said mid-point. In the described preferred embodiment, the absorber is a flattened pipe for conducting therethrough a heat-transfer fluid medium to be heated by the solar radiation, the flattened pipe having a height:width ratio in the range of 2.5:1 to 3.5:1.