This paper discusses ultrahigh-voltage (UHV) DC as an efficient solution for bulk power transmission especially of renewable energy. The European policy and legal framework is used to illustrate how this new technology, international electricity market integration, and the distribution of wind and solar natural resources lead to the need for continent-wide internationally coordinated network planning with a view on long-term greenhouse gas reduction. First, the technical and economic aspects of UHV transmission are described, including, e.g., converter configurations and internal and external insulation. Then, UHV transmission is put into the context of other broad current questions of power system development: AC and DC, microgrids, smart grids, power electronics, overhead lines, cables, and gas-insulated lines. The final part discusses the European legal framework for climate protection and for transmission system operator (TSO) cooperation in the new, legally mandated European transmission system operator association ENTSO-E, in particular for joint European grid planning and for R&D. This example shows how UHV technology development can contribute to market integration and economic and environmental goals for continent-wide and internationally coordinated transmission development as one option in international long-term system studies.