Adna Romanza Chaffee (April 14, 1842 – November 1, 1914) was a lieutenant general in the United States Army. Chaffee took part in the American Civil War and Indian Wars, played a key role in the Spanish–American War, and fought in the Boxer Rebellion in China. He was the Chief of Staff of the United States Army from 1904 to 1906, overseeing far-reaching transformation of organization and doctrine in the army.