Alexander Armstrong III (June 28, 1877 – November 20, 1939) was an American politician and lawyer from Maryland.

He was president of The Armstrong Company, a manufacturer of putties and plastic cements, in Detroit, Michigan.

[4][3] Armstrong was director and a member of the executive committee of the board of the Chesapeake and Potomac Telephone Company.

He was a director of the Baltimore Library Association and a member of the board of visitors of the Severn School.

[1] Armstrong died on November 20, 1939, at his house on Boyce Avenue in Ruxton, Baltimore County.

[2][4] Armstrong received an honorary Doctor of Laws degree from the University of Maryland in 1923.