Jakób Gieysztor (Lithuanian: Jokūbas Geištoras; 18 April 1827 – 15 November 1897) was a Polish-Lithuanian nobleman and politician who participated in the January Uprising of 1863.

Gieysztor's father, Stanisław, is mentioned as a president of the land courts and an active member of the Kaunas insurgent committee in the November Uprising of 1831.

Gieysztor mentions his grandfather's brother, Dominik, as a member of the Great Sejm, where he "called for the treasury and the army", and later entered into the list of the Warsaw townspeople on 29 April 1791.

Gieysztor's maternal grandfather, Ignacy or Peter Zawisza, was a pulkownik during the Kościuszko Uprising that was later deported to Archangelsk.

In 1812 he was chosen as a courier of the Sejm, and a day before his daughter's (Gieysztors mother Leokadja) wedding, he was arrested and imprisoned first in St. Petersburg and then in Warsaw.

Gieysztor began developing an interest in book collection at the age of thirteen with the works of Marcin Bielski and Julian Ursyn Niemcewicz.

[1][4] In 1848, right before the final exam, Gieysztor returned to Lithuania to stop insurrectionist activities of the Lithuanian Youth Fraternity Union.

Gieysztor then turned to farming and settled in the estate of the Ignacygrad manor belonging to his late grandfather in the Kedainiai district, which he inherited.

They had five sons and one daughter: Stanisław Igancy Stefan, Kazimierz Dominiki Adam, Tadeusz Franciszek Alfons, Jan, Witold, and Leokadia.

The fourth part is considered the most important, as it covers the uprising, land reforms, inner politics as well as Gieysztor's arrest.