Count Gustav Horn (October 22, 1592 – May 10, 1657) was a Swedish nobleman of Finnish descent, military officer, and Governor-General.

He was appointed member of the Royal Council in 1625, Field Marshal in 1628, Governor General of Livonia in 1652 and Lord High Constable since 1653.

He was High Councillor of the realm in 1625, elevated to the rank of field marshal in 1628, and sometimes commander-in-chief of Swedish forces in Germany during Thirty Years' War.

He was born into the Swedish (geographically and ethnically Finnish) noble family Horn af Kankas and was educated extensively in European universities.

At the Battle of Breitenfeld in 1631, Horn prevented the Imperial force under Tilly from flanking the main body of the Swedish army, after their Saxon allies had fled the field.

After this Horn led troops in Upper (southern) Franconia and conquered among others, Mergentheim, the town of the Teutonic Order and the bishopric of Bamberg).

[3] After the death of King Gustav II Adolf at Lützen in November 1632, Field Marshal Horn and General John Banér were appointed to the overall command of Swedish forces in Germany.

When Horn was ordered to combine his troops with those of Bernhard of Weimar, the two men found themselves unable to work together, and they were given separate commands.

After Wallenstein's murder in 1634, Horn took some areas in Swabia: in the spring of that year, his troops unsuccessfully laid siege to the imperial city of Überlingen, which would have been a rich and valuable prize.