A2SEA was an offshore wind farm installation and services company based in Fredericia, Denmark.

The company's first installation work was the Horns Rev 1 wind farm in the North Sea in 2002.

In 2010, it was announced that Siemens Wind Power will acquire a 49% stake in the company at a price of DKK 860m.

[6] In 2017, A2SEA was sold to GeoSea, a Belgian offshore installation company member of the DEME Group.

[2][9] In early 2016 the barge Sea Worker was grounded off Nymindegab, Denmark after its tow cable broke during bad weather.