Count Carl Gustav Rehnskiöld (6 August 1651 – 29 January 1722) was a Swedish Field Marshal under the command of King Karl XII of Sweden. Despite being choleric and irritable, Rehnskiöld's military skills made him the chief military adviser and second-in-command to King Karl and earned him the epithet the "Parmenio of the Northern Alexander."
Rehnskiöld was born in Stralsund, the son of Gerd Antoni Rehnskiöld and Birgitta Torskeskål.
During his life, he played an important role in the Great Northern War. He commanded at the Battle of Fraustadt, after which King Karl XII made him a Field Marshal and Count. Highlights of his career include a highly successful campaign against Poland from 1701-1703, and the disastrous Ukrainian campaign which ended with the Battle of Poltava in 1709. The battle was a catastrophe for the Swedish army and Rehnskiöld was captured by the Russians. He remained in Russian captivity until 1718.