Calvin Coolidge (born John Calvin Coolidge Jr.; ; July 4, 1872 – January 5, 1933) was an American attorney and politician who served as the 30th president of the United States from 1923 to 1929.

Born in Vermont, Coolidge was a Republican lawyer from New England who climbed the ladder of Massachusetts politics, becoming the state's 48th governor; his response to the Boston Police Strike of 1919 thrust him into the national spotlight as a man of decisive action. The next year, Coolidge was elected the country's 29th vice president and succeeded the presidency upon the sudden death of President Warren G. Harding in 1923. Elected in his own right in 1924, Coolidge gained a reputation as a small-government conservative with a taciturn personality and dry sense of humor that earned him the nickname "Silent Cal". Though his widespread popularity enabled him to run for a second full term, Coolidge chose not to run again in 1928, remarking that ten years as president would be "longer than any other man has had it – too long!"

Throughout his gubernatorial career, Coolidge ran on the record of fiscal conservatism, strong support for women's suffrage, and a vague opposition to Prohibition. During his presidency, he restored public confidence in the White House after the many scandals of the Harding administration. He signed into law the Indian Citizenship Act of 1924, which granted U.S. citizenship to all Native Americans, and oversaw a period of rapid and expansive economic growth known as the "Roaring Twenties", leaving office with considerable popularity. He was known for his hands-off governing approach and pro-business stances; as biographer Claude Fuess wrote: "He embodied the spirit and hopes of the middle class, could interpret their longings and express their opinions. That he did represent the genius of the average is the most convincing proof of his strength."

Scholars have ranked Coolidge in the lower half of U.S. presidents. He gains nearly universal praise for his stalwart support of racial equality during a period of heightened racial tension in the United States, and is highly praised by advocates of smaller government and laissez-faire economics, while supporters of an active central government generally view him less favorably. His critics argue that he failed to use the country's economic boom to help struggling farmers and workers in other flailing industries, and there is still much debate among historians as to the extent to which Coolidge's economic policies contributed to the onset of the Great Depression.