Mabel Costigan (née Cory; 1873–1951) was an American community and church leader and advocate for labor laws for children and foreign-born individuals.

[2] She campaigned for child labor law, particularly interested in prohibiting the practice of using children in sugar beet fields.

[5] Costigan was a suffragist,[4] which was rewarded when the 19th Amendment of the American Constitution that granted women the right to vote was passed by Congress on June 4, 1919, and ratified on August 18, 1920.

She was described in 1926 as one of "two score, diligent, feminine representatives of the organized women of the country who have become the most powerful lobby ever concentrated in the national capital" by Oliver P. Newman, Former President of the Board of Commissioners of the District of Columbia.

Costigan was said to have been a notable and hard-working presence in Washington, D.C., since World War I. Selma Borchardt, who represented the American Federation of Teachers, was the other of two women said to be highly effective.

[7] In 1924, she campaigned for Robert M. La Follette, the Progress Party's presidential candidate, speaking to thousands of women workers in New York, Massachusetts, and Rhode Island.

[9] With Jeanne Rankin, she led a coalition of 3,000 women that pressured the Republican and Democratic parties to add the issue of peace to their platforms in 1932.