Hans Theodor Woldsen Storm, commonly known as Theodor Storm, was a German-Frisian writer. He is considered to be one of the most important figures of German realism.

Sir Theodore Andrea Cook was a British art critic and writer.

Theodore Ayrault Dodge was an American officer, military historian, and businessman. He fought as a Union officer in the American Civil War; as a writer, he was devoted to both the Civil War and the great generals of ancient and European history.

Theodore Clarke Smith (1870–1960) was professor of American history at Williams College from 1903 to 1938. Smith was an educationalist and curriculum reformer who served on the Committee on Curriculum of 1911-1927 and the Advisory Committee of 1911-1935.

Theodore Herman Albert Dreiser was an American novelist and journalist of the naturalist school. His novels often featured main characters who succeeded at their objectives despite a lack of a firm moral code, and literary situations that more closely resemble studies of nature than tales of choice and agency. Dreiser's best known novels include Sister Carrie (1900) and An American Tragedy (1925).

George Edwards Theodore Goodridge Roberts was a Canadian novelist and poet. He was the author of thirty-four novels and over one hundred published stories and poems.

Theodore Edward Hook was an English man of letters and composer and briefly a civil servant in Mauritius. He is best known for his practical jokes, particularly the Berners Street hoax in 1809. The world's first postcard was received by Hook in 1840; he likely posted it to himself.

Theodore Ledyard Cuyler was an American Presbyterian minister and writer.

Theodore Parker was an American transcendentalist and reforming minister of the Unitarian church. A reformer and abolitionist, his words and popular quotations would later inspire speeches by Abraham Lincoln and Martin Luther King Jr.

Theodore Roosevelt Jr., often referred to as Teddy or by his initials, T. R., was an American politician, statesman, soldier, conservationist, naturalist, historian, and writer who served as the 26th president of the United States from 1901 to 1909. He previously served as the 25th vice president under President William McKinley from March to September 1901 and as the 33rd governor of New York from 1899 to 1900. Assuming the presidency after McKinley's assassination, Roosevelt emerged as a leader of the Republican Party and became a driving force for anti-trust and Progressive policies.