The surname Ossowski (singular masculine), Ossowska (singular feminine), or Ossowscy (plural) (also Osowski / Osowska / Osowscy) belongs to a Polish noble family. The name derives from the Polish place-name Ossowy, with the suffix -ski indicating land-ownership or lordship. Variants of the name include Ossowskiego, Ossowskich, and Ossowskliéj; the German or Prussian equivalent sometimes appears as von Ossowski. The family originally belonged to the clan Dołęga but began to use the present surname in the 14th or 15th century.
The Ossowski family is believed to have originated from Poznań in the 13/14th century (see talk page). There they were in service to the Senat, with royal appointments under the Przywilej koszycki, held for life and only subject to recall upon conviction of high treason. Later the family spread from Poznań to found several villages around Poznań and Wschowa, where Hincza Ossowski and his son military General Mikolaj Dołęga-Ossowski founded the Village of Osowa Sień.
According to legend, King Boleslaw Krzywousty (1102–1139) won a victory over the Prussians with the help of a bowman named Dołęga, inspiring a popular uprising. Dołęga was rewarded with an arrow as an augmentation to his Pobóg arms, and the resulting coat of arms was named after him. The Dołęga clan was famous for the precision of their bowmen and the bravery of their cavalry. The Ossowskis was one of the first families to receive the title, and may have connections to this legendary knight.
Jan Dołęga-Ossowski is believed to be the founder of the Ossowski noble family (szlachta). He had some connection to John Ossowski of Szczecin-Osów, who received recognition from King Louis I of Hungary for victualling the army when it arrived in his territory in 1374. Komes/Hrabia Dołęga-Ossowski also owned a manor house in the village of Szczecin-Osów and was a member of the Polish Order of the Virtuti Militari.