Alphonso Taft (November 5, 1810–May 21, 1891) was the Attorney General and Secretary of War under President Ulysses S. Grant.

Born in Townshend, Vermont, he graduated from Yale College in 1833, where he also was a tutor. At Yale, he and his classmate William Huntington Russell co-founded Skull and Bones, a secret society that exists to this day. He subsequently studied law at the Yale Law School, was admitted to the Connecticut bar in 1838, removed to Cincinnati in 1839 where he was a member of the Cincinnati City Council, and became one of the most influential citizens of Ohio. He was a member of the boards of trustees of the University of Cincinnati and of Yale College.

He made an unsuccessful run for the United States House of Representatives in 1856. He was a judge of the Superior Court of Cincinnati from 1866 to 1872. Taft was appointed Secretary of War by President Grant in March, 1876, and three months later Attorney General of the United States.

After he left office as Attorney General in 1877 he returned to the practice of law. He was an unsuccessful candidate for Governor of Ohio in 1875 and 1879. Taft was ambassador to Austria-Hungary in 1882, and to the Imperial Russia from 1884 to 1885.

Alphonso Taft died in San Diego, California, on May 21, 1891.

His son, William Howard Taft I, was the 27th President of the United States; both his grandson and great-grandson, Robert A. Taft I and Robert Taft Jr., were senators; his great-great-grandson, Robert A. Taft III, is the current Governor of Ohio. William Howard Taft III was ambassador to Ireland; William Howard Taft IV advises the State Department.

|- style="text-align: center;" | width="30%" |Preceded by:
Edwards Pierrepont | width="40%" style="text-align: center;" |United States Attorney General
1876–1877 | width="30%" |Succeeded by:
Charles Devens