Großostheim (or Grossostheim) is a market community in the Aschaffenburg district in the Regierungsbezirk of Lower Franconia (Unterfranken) in Bavaria, Germany.

Großostheim lies on the northeast edge of the Odenwald in the Bavarian Lower Main (Bayerischer Untermain) region.

Ostheim, called Großostheim since the 18th century – groß is German for “great” or “big” – had its first documentary mention in a document from the Fulda Abbey dating from sometime between 780 and 799.

Ostheim belonged from the time of its first documentary mention to various lordly domains, before it passed along with the whole Bachgau to the Electorate of Mainz.

The new Ringheim arose after 1945 on the lands of the former Luftwaffe base, in whose barracks and other buildings Germans driven out of their homelands were housed.

The village had, however, surely been settled much earlier, as the many archaeological finds from Wenigumstadt show a human presence from every cultural epoch in the last 7,000 years.

The former (until 1782) Electoral Mainz Vogteiamt (Vogt district) became in 1803 part of Archbishop-Elector of Mainz Karl von Dalberg's newly formed Electorate of Aschaffenburg, along with which, under the terms of the Treaties of Paris, it passed in 1814 (by this time it had become a department of the Grand Duchy of Frankfurt) to Bavaria.

The community's arms might be described thus: Party per fess Or and sable, a buck salient of the second langued gules and couped at the thigh, and three trefoils slipped argent.

The coat of arms, conferred on 17 January 1911 by Prince Regent Luitpold and borne ever since, is a combination of the 17th-century community seal, which is no longer on hand, and a smaller version of the arms borne by the family Schad, whose members called themselves Schad von Ostheim.