Theodore J. Schaffer (born April 25, 1857) was president of the Amalgamated Association of Iron, Steel, and Tin Workers, republican, Methodist.
He was employed by the same company for a time in a new mill at Scottdale, Pennsylvania, but returned and again worked at the Penn forge.
After serious health problems, he spent two years each in Washington and Butler counties, holding two charges in each and preaching on alternate Sundays.
From August, 1889 to October, 1894, he was employed as a steel rougher and roller in the Demmler mill of the United States sheet steel and tin plate company, and, after an idleness of eleven months, became roller in the tin mill of Oliver Bros, in Pittsburgh, working there until April, 1897, part of the time as acting manager.
In April, 1897, Shaffer was placed in the presidency of Amalgamated Steel by the advisory board of the association, was elected to the position a month later.