Baron Geert von Innstetten is a fictional character from the novella "Effi Briest," written by Theodor Fontane. He is portrayed as a well-educated and ambitious Prussian nobleman who marries the young protagonist, Effi Briest. His character embodies the values and social expectations of the 19th-century German aristocracy. In the story, von Innstetten's strict adherence to societal norms and his sense of duty lead to conflicts in his marriage. His character ultimately represents the struggles between personal desires and societal obligations, highlighting the themes of romanticism and realism in literature.