Offshore wind power or offshore wind energy-use of wind farms constructed offshore,

Offshore wind power or offshore wind energy is the use of wind farms constructed offshore, usually on the continental shelf, to harvest wind energy to generate electricity. Stronger wind speeds are available offshore compared to on land, so offshore wind power’s contribution in terms of electricity supplied is higher, and NIMBY opposition to construction is usually much weaker. However, offshore wind farms are relatively expensive. At the end of 2014, 3,230 turbines at 84 offshore wind farms across 11 European countries had been installed and grid-connected, making a total capacity of 11,027 MW.

As of 2010 Siemens and Vestas were turbine suppliers for 90% of offshore wind power, while Dong Energy, Vattenfall and E.on were the leading offshore operators.As of 1 January 2016, about 12 gigawatts (GW) of offshore wind power capacity was operational, mainly in Northern Europe, with 3,755 MW of that coming online during 2015.[4] According to BTM Consult, more than 16 GW of additional capacity will be installed before the end of 2014 and the United Kingdom and Germany will become the two leading markets. Offshore wind power capacity is expected to reach a total of 75 GW worldwide by 2020, with significant contributions from China and the United States.

As of 2013 the 630 megawatt (MW) London Array is the largest offshore wind farm in the world, with the 504 (MW) Greater Gabbard wind farm the second largest, followed by the 367 MW Walney Wind Farm. All are off the coast of the UK. These projects will be dwarfed by subsequent wind farms that are in the pipeline, including Dogger Bank at 4,800 MW, Norfolk Bank (7,200 MW), and Irish Sea (4,200 MW). At the end of June 2013 total European combined offshore wind energy capacity was 6,040 MW. UK installed 513.5 MW offshore windpower in the first half year of 2013.

Offshore wind power refers to the construction of wind farms in bodies of water to generate electricity from wind. Unlike the typical usage of the term "offshore" in the marine industry, offshore wind power includes inshore water areas such as lakes, fjords and sheltered coastal areas, utilizing traditional fixed-bottom wind turbine technologies, as well as deep-water areas utilizing floating wind turbines.

Europe is the world leader in offshore wind power, with the first offshore wind farm (Vindeby) being installed in Denmark in 1991. In 2013, offshore wind power contributed to 1,567 MW of the total 11,159 MW of wind power capacity constructed that year. By January 2014, 69 offshore wind farms had been constructed in Europe with an average annual rated capacity of 482 MW in 2013,and as of January 2014 the United Kingdom has by far the largest capacity of offshore wind farms with 3,681 MW. Denmark is second with 1,271 MW installed and Belgium is third with 571 MW. Germany comes fourth with 520 MW, followed by the Netherlands (247 MW), Sweden (212 MW), Finland (26 MW), Ireland (25 MW), Spain (5 MW), Norway (2 MW) and Portugal (2 MW).By January 2014, the total installed capacity of offshore wind farms in European waters had reached 6,562 MW.

As of January 2014, German wind turbine manufacturer Siemens Wind Power and Danish wind turbine manufacturer Vestas together have installed 80% of the world's 6.6 GW offshore wind power capacity; Senvion-REpower comes third with 8% and Bard (6%).

Projections for 2020 calculate a wind farm capacity of 40 GW in European waters, which would provide 4% of the European Union's demand of electricity.

The Chinese government has set ambitious targets of 5 GW of installed offshore wind capacity by 2015 and 30 GW by 2020 that would eclipse capacity in other countries. In May 2014 current capacity of offshore wind power in China was 565 MW.

India is looking at the potential of off-shore wind power plants, with a 100 MW demonstration plant being planned off the coast of Gujarat (2014). In 2013, a group of organizations, led by Global Wind Energy Council (GWEC) started project FOWIND (Facilitating Offshore Wind in India)to identify potential zones for development of off-shore wind power in India and to stimulate R & D activities in this area FOWIND. In 2014 FOWIND commissioned Center for Study of Science, Technology and Policy (CSTEP) to undertake pre-feasibility studies in eight zones in Tamil Nadu which have been identified as having potential.