Jacob von Eggers (before 1772 Jacob Eggers; 14 December 1704 – 12 January 1773) was a military engineer and Swedish friherre (baron). He was born in a German-speaking family in present-day Tartu, then known as Dorpat, in Russian-occupied Swedish Livonia, during the Great Northern War. Around the age of four he was deported together with his mother to Russia, where in 1713 she remarried a Swedish baron who was a prisoner of war there. After the war, the family moved to Sweden where Jacob pursued studies in fortification. He became an officer in the Swedish military in 1729. Following his stepfather's death in 1733, he sought opportunities to further his career abroad as well as in Sweden. In 1734 he accompanied the troops of Stanisław Leszczyński during the War of the Polish Succession and participated in the siege of Danzig (modern-day Gdańsk). He then spent some time as a volunteer in imperial, Saxon and French service, as well as making study trips around Europe. From 1737 he formed a more lasting link with the Electorate of Saxony, and was formally employed both by the Swedish and Saxon militaries until 1758.
He participated in several campaigns during these years, and wrote an appreciated account of the French siege and capture of Bergen op Zoom in 1747. He went on to further edit and expand a French military dictionary, and provide an influential and expanded German translation of the same work. He was furthermore entrusted with the military education of the Saxon princes Charles and Xavier. He was promoted in both Swedish and Saxon service, ending the latter with the rank of major general in 1757. In Sweden, he was elevated to the rank of friherre or baron, awarded the Order of the Sword and elected a member of the Royal Swedish Academy of Sciences. In 1758 Jacob von Eggers however left both Swedish and Saxon service and settled in Gdańsk, where he would spend the rest of his life as commander of the city's fortifications. He kept in contact with the Swedish academy, and donated his extensive library to it. He died in 1773.