AUGUSTUS PEABODY GARDNER (November 5, 1865 – January 14, 1918) was born in Boston to Joseph Peabody Gardner and Harriet Sears Amory. He was the descendant of Thomas Gardner (planter) and nephew of John "Jack" Lowell Gardner II whose wife was Isabella Stewart Gardner. Jack and Isabella 'adopted' Augustus and his two brothers (Joseph and William) after the death of their father in 1875. Their mother had died in 1865.

He received his early education at Hopkinson's School in Boston and at St. Paul's School, Concord, New Hampshire, and graduated from Harvard in 1886. After graduation he made his permanent home in Hamilton and was in business in Boston. In 1892 he married Constance Lodge, only daughter of Senator Henry Cabot Lodge, at Saint Anne's Church, Nahant, Massachusetts.

In 1898, at the outbreak of the war with Spain, he received a Commission as Captain and Assistant Adjutant-General, and was assigned to the Staff of Major-General James H. Wilson. He served in the Porto Rican campaign and was recommended for a Brevet Majority, " for gallant and meritorious services," though he did not actually receive his Brevet rank till some years afterwards.

Gardner was elected a member of the Massachusetts Senate in 1899 and served from 1900 to 1901. He was elected, as a Republican, to the Fifty-seventh Congress by special election, after the resignation of United States Representative William H. Moody. He was reelected to the eight succeeding Congresses (November 4, 1902 – May 15, 1917). He was the chairman of the Committee on Industrial Arts and Expositions during the Fifty-ninth and Sixtieth Congresses.

At the beginning of World War I, Gardner's Sister in law, Mrs. George Cabot Lodge and her children Henry, John, and Helene were stranded in France. In August 1914 Gardner traveled to France to extract the Lodges, and brought them to safety in London.

Gardner resigned from Congress to enter the army. During the First World War, he served at Governors Island. He was colonel in the Adjutant General’s Department, and later was transferred at his own request to the One Hundred and Thirty-first Regiment, United States Infantry, with the rank of major. He died of pneumonia while on active duty at Camp Wheeler on January 14, 1918 and was buried at Arlington National Cemetery.