John Quincy Adams II (September 22, 1833 – August 14, 1894) was an American politician who represented Quincy in the Massachusetts House of Representatives from 1866 to 1867, 1868 to 1869, 1871 to 1872, and from 1874 to 1875.

Adams served as a colonel in the Union Army during the American Civil War under Governor John Albion Andrew of Massachusetts. Later in life, he left the Republican Party in 1867 for the Democratic Party.

John Quincy Adams II was born on September 22, 1833, in Boston, Massachusetts, the second of seven children born to Charles Francis Adams Sr. and Abigail Brown Adams.

He was a grandson of the sixth United States president, John Quincy Adams (his namesake), and a great-grandson of the second president, John Adams. His maternal grandfather was shipping magnate Peter Chardon Brooks (1767–1849).

He graduated from Harvard University in 1853, studied law, and two years later was admitted to the Suffolk County bar, and practiced in Boston. He followed his profession for a short time, then, becoming interested in agriculture, he established an experimental model farm of five hundred acres near Quincy, Massachusetts.

During the Civil War he served as an aide-de-camp on the staff of Governor John Albion Andrew, first as a lieutenant colonel, and later as a colonel. During the war his duties included visiting Massachusetts units in the field and providing the governor status reports on their condition. In 1862, he made inspection visits to several Massachusetts units operating in North Carolina.

Adams served in several local offices in Quincy, including town meeting moderator, school board chairman and judge of the local court. He was elected to the Massachusetts state legislature as a Republican, but soon switched to the Democratic Party because of his dissatisfaction with Republican Reconstruction policies. In addition to serving in the Massachusetts House of Representatives in 1865, 1867, 1870 and 1873, he was the unsuccessful Democratic nominee for Governor of Massachusetts in every year from 1867 to 1871. (Governors served one year terms until 1918.)

Adams received one vote for the Democratic nomination for President of the United States at the 1868 Democratic National Convention. In 1872, the faction of Democrats that refused to support Horace Greeley, the fusion candidate of Democrats and the Liberal Republican Party, nominated Charles O'Conor for president and Adams for vice president on the "Straight-Out Democratic" ticket. They declined, but their names remained on the ballot in some states.