This is for the Canadian businessman and politician. For other people named James Reilly, see James Reilly.

James A. Reilly is a Canadian businessman and politician. He was the sixth and twelfth mayor of Calgary, Alberta. He was married to May Watts.

Reilly was born in 1835 in Naperville, Quebec to immigrants from Ireland. In Quebec he became an architect and builder before going to Winnipeg, Manitoba in 1882 then to Calgary in 1883. In Calgary he became actively involved with the local community. He played a key part in organizing a citizens group concerned about the location of the railway station that was built in Calgary. While proprietor of the Royal Hotel, he organized the first civic committee meeting on January 4, 1884. This was the first step leading to Calgary's municipal incorporation later that year.

Reilly ran in Calgary's second mayoral election in 1885, but was defeated by popular incumbent George Murdoch. On January 19, 1891, he was elected as the sixth mayor of Calgary. He served one term, but then was re-elected a few years later as the twelfth mayor. Reilly also served two years on city council. As a member of the Liberal Party of Canada, Reilly unsuccessfully ran for federal politics.

In October of 1899, Reilly left Calgary and travelled extensively. He retired in Victoria, British Columbia, where he died on July 9, 1909 of influenza.