politician Lord High Steward of Sweden
Born either in Tyresö, Sweden, or in Reval (modern Tallinn, Estonia), he was the son of Privy Councillor Gustaf Gabrielsson Oxenstierna and Barbro Axelsdotter Bielke. From 1612 he was chancellor and chief adviser of Duke John, son of former King John III.
Oxenstierna began studying in Uppsala. He continued to study abroad, in German towns Rostock, Wittenberg and Jena. After his return to Sweden, he was in the service of King Charles IX from 1604.
Also in 1612, Oxenstierna was appointed governor of Estonia.
In 1617 he became a Privy Councillor and a marshal of the court of King Gustavus Adolphus. Being a close confidant of older brother Axel Oxenstierna (Lord High Chancellor 1612-1654) as well as of the king, Gabriel Oxenstierna was used as a diplomatic representative on numerous occasions.
He was sent as a legate to Denmark both in 1622 and 1625, and during the latter year he also visited Lübeck, Hamburg, Mecklenburg, Brandenburg, Pomerania, the Netherlands and England. Gabriel then became responsible to transport the body of the king back to Sweden.
In 1634, he became Lord High Steward (riksdrots), making him head of Svea Court of Appeal (Svea Hovrätt) and as such supervisor of justice in Sweden.
In 1611, Oxenstierna married Märta Bielke, daughter of Privy Councillor Ture Bielke and Margareta Sture. Oxenstierna has been described as "reasonable, honest, jovial and outspoken, loved by high and low". After inheriting Tyresö in the 1620s, Oxenstierna ordered a reconstruction of Tyresö Palace as well as the building Tyresö Church.
The church was inaugurated with his own burial in 1641.
