The Gotha Research Library preserves over 11,500 manuscripts of European and Oriental provenance, representing around 1,300 years of different manuscript cultures. It continues to acquire manuscripts and bequeathed materials according to its collection profile.
Since the foundation of the library in 1647, the collection has been successively expanded through acquisitions and donations. The efforts of Duke Ernst I (1601–1675), who brought manuscripts as looted art during the Thirty Years' War from Mainz, Würzburg and Munich to Gotha, deserve special mention. Duke Ernst II (1745-1804) acquired numerous precious manuscripts, buying some 50 valuable mediaeval pieces from such important monasteries and scriptoria as Echternach and Murbach from the enterprising French Benedictine monk Jean-Baptiste Maugérard (1735–1815). A large part of the collection of oriental manuscripts was also acquired in the Orient on his behalf by Ulrich Jasper Seetzen (1767–1811). Another core collection encompasses more than 11,130 emigrant letters that have been collected since the 1980s at the instigation of Prof. Wolfgang Helbich and scientifically supervised by Prof. Ursula Lehmkuhl.
The main focus of the manuscript collection is on early modern manuscripts, which were acquired primarily by the ducal house of Saxe-Gotha-Altenburg. The core of the manuscript collection is formed by the so-called Reformation manuscripts, originating in the 16th century and compiled primarily under Duke Ernst I and Duke Friedrich II of Saxe-Gotha-Altenburg. The manuscript collection has no specific focus, which means that it aptly reflects the knowledge of the early modern period in all its rich facets. In addition, around 1,400 musical records document the rich musical life of the time, including works by the Bach family of composers and the Gotha court orchestra as well as pieces related to Bohemian and Thuringian music history.