The 1904 United States presidential election was the 30th quadrennial presidential election, held on Tuesday, November 8, 1904. Incumbent Republican President Theodore Roosevelt defeated the conservative Democratic nominee, Alton B. Parker. Roosevelt's victory made him the first president who ascended to the presidency upon the death of his predecessor to win a full term in his own right. This was also the second presidential election in which both major party candidates were registered in the same home state; the others have been in 1860, 1920, 1940, 1944, and 2016.

Theodore Roosevelt Jr., often referred to as Teddy or by his initials, T. R., was an American politician, statesman, conservationist, naturalist, and writer who served as the 26th president of the United States from 1901 to 1909. He previously held various positions in New York politics, rising up the ranks to serve as the state's 33rd governor for two years. He later served as the 25th vice president under President William McKinley for six months in 1901, assuming the presidency after McKinley's assassination. As president, Roosevelt emerged as a leader of the Republican Party and became a driving force for anti-trust and Progressive policies.