Thomas Gold Appleton (March 31, 1812 – April 17, 1884), son of merchant Nathan Appleton and Maria Theresa Gold, was an American writer, an artist, and a patron of the fine arts. Henry Wadsworth Longfellow became his brother-in-law after marrying Appleton's sister Frances.
Appleton was born on March 31, 1812, in Boston, Massachusetts; he would later joke that he just missed being born an April fool. He graduated from Harvard College in 1831 and in October 1838 was admitted to the bar in Suffolk County, Massachusetts; he set up his office on Tremont Row. He became known for his witticisms, one of which, the oft-quoted "Good Americans, when they die, go to Paris", is sometimes attributed to Oliver Wendell Holmes. Appleton and Holmes met in 1833 on their way to Paris.
Appleton befriended the poet and professor Henry Wadsworth Longfellow during a trip to Europe in the 1830s; the two became close friends. Later, back in Massachusetts, Appleton encouraged Longfellow to pursue his sister Frances Appleton. In fact, Frances took several years before she was convinced to marry Longfellow; in the meantime, Thomas Appleton maintained a good friendship with Longfellow. When Appleton prepared for a trip to Europe, Frances implied that she would need company in his absence, suggesting she had consented to marriage. The couple's wedding in 1843 was held at the Appleton home in Beacon Hill.
Appleton spent much of his life traveling. As he wrote, "More and more the world needs, and learns to value, its vacation". He visited Niagara Falls in 1842, for example. On another vacation in the 1840s, Appleton met Horace Mann and took him dancing at the Champs-Élysées in Paris. He wrote to his brother-in-law, "You may conceive the length of face with which the leader of Normal instructors contemplated the Can-Can". Also in Paris, Appleton developed an interest in spiritualism and mesmerism.